state-owned enterprises play an important role in the implementation of China"s economic development and innovation development strategy. Under the background of comprehensively deepening reform and high-quality economic development, the mixed ownership reform of state-owned enterprises has been raised to a new height and given a new mission. State owned enterprises are innovation pioneers in some major fields and undertake more basic research work. Therefore, it is not enough to study the innovation behavior of state-owned enterprises only from the level of innovation investment quantity, but also from the level of quality. Based on the data of A-share listed companies in Shenzhen and Shanghai from 2008 to 2019, this paper studies the impact of mixed ownership reform on innovation decision-making of state-owned enterprises. The conclusions are as follows: (1) the change of ownership structure has no significant impact on exploration innovation investment of state-owned enterprises. (2) The positive impact of equity diversity on exploitation innovation investment is more significant in competitive state-owned enterprises and state-owned enterprises with higher absorbed redundant resources. (3) The negative impact of the proportion of non-state-owned shares on the investment of exploitation innovation can be alleviated in the state-owned enterprises with high degree of industry competition and the state-owned enterprises with higher absorbed redundant resources. These findings not only provide policy reference for the implementation of mixed ownership reform policy, but also provide reference for the innovation decision-making of state-owned enterprises.