Abstract: One of the important characteristics of R&D investment is the high adjustment cost. The stability and continuity of R&D funds have an important impact on business operations. Focusing on the stability of R&D investment, the balanced panel data of Chinese A-share high-tech enterprises from 2014 to 2018 was used as the research sample, and the system generalized method of moments (SGMM) was used to test the relationship between corporate life cycle, industry competition level and R&D smoothing behavior. The study found that: (1) The amount of change in the cash holdings of the sample companies is significantly negatively correlated with the R&D investment scale. China’s high-tech enterprises have the situation of smoothing R&D expenditure by holding internal cash flow; (2) The R&D smoothing behavior varies among enterprises in different life cycles. It is significant in mature enterprises, but not in growing and declining enterprises; (3) The level of industry competition can significantly adjust the R&D smoothing behavior of enterprises. The smooth effect of cash holdings on R&D investment becomes more pronounced as the level of industry competition increases.