Abstract: The mutual interaction and transformation between science and technology have become an important link in the development of science and technology, and it constitutes the premise of long-term economic growth. However, there is outdated science and technology management system left from the planned economy in China. It not only leads to the high cost and the poor effect of coupling between science and technology, but also reduces the pushing effect of science and technology’s development on economic growth in the long run. So the sci-tech management system should be improved. Based on recent national initiative, it is necessary for scientific research department and technological research department to focus on the division of functions respectively, and attach great importance to the effect of coupling between science and technology on economic growth comprehensively. At the same time, the path dependence on R&D management functions needs to be changed by the government departments. Their service awareness on scientific and technological innovation activities should be self-improved. Therefore, exploring the path, which can promote the economic growth rate from the perspective of the coupling effect of science and technology, is conducive to deepening the understanding of the fusion of science, technology and economy. It’s of great practical significance to improve the innovative service capacity of the government.It has been obtained that science and technology can exert positive and long-term effects on economic growth. So as to investigate the difference of this effect in diverse coupling paths, the coupling path of science and technology should be divided. They can be divided into six types in theory according to three kinds of relationship between science and technology. They are reconfigured by the coupling strength, which can be divided into sci-strong path, tech-strong path and sci-tech-balanced path, and by the coupling cost rate, which can be divided into the path with low cost rate and with high cost rate. That is to say, they are sci-strong path with low cost rate and with high cost rate, tech-strong path with low cost rate and with high cost rate and sci-tech-balanced path with low cost rate and with high cost rate.Meanwhile, the Romer endogenous growth model is extended by endogenizing science and by introducing the departments of innovative service and the human capital development. So the entire economy is divided into six departments, which are final product department, intermediate product department, scientific research department, technological research department, innovation service department and human capital development department. In order to obtain the optimal coupling path to improve economic growth, the dynamic programming problem needs to be solved after related parameters are controlled and related conditions are constrained. The problem is solved by using balanced-growth-path analysis, and two kinds of relationships between the coupling path and economic growth are obtained. One is the effect of the coupling paths, divided by the coupling strength, on economic growth. It tells us how to judge from the parameters’ selection to put forward the long-term and short-term strategy for the development of science and technology. The long-term strategy should be formulated based on some conditions met. The short-term strategy can be obtained according to whether science or technology can push economic growth in the short run or not. The other is the effect of the paths with low cost rate and high cost rate on economic growth. It shows us how the influence of scientific growth rate and technological growth rate on economic growth rate is changing in different coupling paths.Numerical simulations on these relationships are preceded by taking China as the research object. Results show that effective adjustment of the coupling cost rate is conducive for sci-strong path with low cost rate to promote the economic growth of China in a short term, while the sci-tech-balanced path with low cost rate is more suitable for long-term strategy for innovation and economic development. That is to say, the development of science and technology of our country should transform from the sci-strong path for the short-term decision to the sci-tech-balanced path for the long-term strategy. In addition, the empirical results also show that, during the transition of path transforming, the government should control the coupling cost in the sci-strong path effectively, and take corresponding measures to reduce the coupling cost in the sci-tech-balance path. So it is the heterogeneity between science and technology that results in the difference of effects of science and technology themselves on economic growth. Therefore, in the optimal path to promote economic growth, the reduction of coupling cost rate will not necessarily lead to the increase of the total impact of science and technology on economic growth of China.Based on the results, some policy recommendations of government functions during the sci-tech management system reform are proposed, which can change government functions from research management to innovative service. Firstly, the sci-strong path with low cost should be born. The government should improve the peer review mechanism and the incentive mechanism of transformation of achievements in scientific research in the first place, and construct scientizing mechanism for the achievements of technology research and development of enterprise in the second, instead of performing the role of supervision. Secondly, the sci-tech-balanced path with low cost should be taken place. Medium-term and long-term evaluation system of scientific research should be improved in a planned way. Not only the allocation mechanism of capital should be set for different kinds of investing objects, but also investing mechanism between scientific and technological research activities should be set for different types of capital self. Besides it is not only necessary to implement the evaluation mechanism of capital between universities, research institutes and enterprises when it is invested, but also to build the evaluation system of transformation between science and technology within the same institution or between different institutions. Thirdly, governments departments should put forward corresponding policies according to the short-term and long-term differences in the sensitivity of the coupling cost rate to enhance the improvement.

Key words: science, technology, coupling path, economic growth model