Abstract: Research and development (R&D) investment is not only the key for enterprises to improve their core competitiveness, but also an important measure for China to solve the "strangle" problem and achieve an innovative national strategy. For a long time, the central and local governments attach great importance to the enterprise R&D behavior encouragement and guidance, especially for the implementation of the national innovation strategies in recent years, such as "innovation driven", "intelligent manufacturing", "public entrepreneurship, peoples innovation". Government subsidies for enterprises research and tax incentive policy is gradually systematized and institutionalized, which effectively promotes the growth of R&D investment. However, with China′s economy entering the stage of "new normal" development after 2013, macroeconomic uncertainties have increased significantly, but the growth rate of R&D investment intensity has slowed down, revealing the importance of macroeconomic cycle fluctuations on R&D investment intensity.Academic circles apply political uncertainty, economic policy uncertainty and observed volatility of specific companies or markets as alternative variables to conduct extensive research on the impact of economic uncertainty on R&D investment. Considering that the economic uncertainty in a specific period is "good" and "bad", and "good" and "bad" uncertainties should have different impact mechanisms on R&D investment. In this paper, the realized volatility, positive half-variance and negative half-variance of the realized volatility of China′s industrial added value growth rate are used to describe the macroeconomic uncertainty, "good uncertainty" and "bad uncertainty" respectively, and the annual data of China′s 1126 listed companies from 2009 to 2019 are selected to carry out panel regression. The influence mechanism and heterogeneity characteristics of economic uncertainty, "good" and "bad" uncertainty on firms′ R&D investment intensity are investigated.The conclusions of are as follows: First, macroeconomic uncertainty has a significant stimulating effect on firm′s R&D investment. "Good" economic uncertainty has a significant inhibiting effect on firm′s R&D investment, while "bad" economic uncertainty has a promoting effect on firm′s R&D investment. Financing constraint has a restraining effect on R&D investment of enterprises. Second, "good" economic uncertainty alleviates the restraining effect of financing which constraints on firm R&D investment, while "bad" economic uncertainty amplifies the restraining effect of financing constraints on firm R&D investment. Third, "bad" economic uncertainty has a significant effect on the R&D investment of state-owned enterprises, but not other enterprises; "good" economic uncertainty has no significant impact on R&D investment of high-tech enterprises, but has a significant positive effect on non-high-tech enterprises. "Bad" economic uncertainty has a significant impact on R&D investment of high-tech enterprises, but not non-high-tech enterprises. "Good" and "bad" uncertainties have no significant impact on R&D investment in the primary and tertiary industries. "Good" economic uncertainties have no impact on R&D investment in the secondary industry, and "bad" economic uncertainties and financing constraints have significant impact.This study has important implications for the implementation of China′s innovation development strategy. Firstly, in the context of structural slowdown of China′s economy, encouraging bottom-up socially driven innovation, stimulating the innovation consciousness of enterprises, encouraging enterprises to improve the research of products with intellectual property rights should be conducted to create brands and expand characteristic industries. Secondly, the incentive policy for scientific and technological research personnel needs to be perfected, and the enterprise research conditions and team construction should be strengthened. Finally, implementing relevant policies to encourage independent innovation of enterprises, conducting follow-up research on innovation support policies and constantly improving the long-term mechanism are of great importance to establish a technological innovation system with enterprises as the main body, the market as the guidance and the combination of production-learning-research.

Key words: economic uncertainty, "good" economic uncertainty, "bad" economic uncertainty, R&D investment intensity