Abstract: How to optimize the R&D investment intensity and avoid the situation of under-investment or over-investment is a practical science problem. In this sense, we combined the endogenous growth theory and empirical analysis to calculate the optimum R&D investment over the past 12 years and the period of 2013 to 2020 in China. The study results show that the return rate of R&D investment was steadily higher than the return rate of invested capital at the present stage. Also, theChinese R&D investment intensity has not reached the optimum level, which means it can be increased continually to stimulate economic growth.

Key words: R&D investment intensity, endogenous growth theory