Abstract:    Innovation is an important driving force to promote highquality economic development. This paper selected the accelerated depreciation policy of fixed assets implemented in 2014 and 2015 as a quasi-natural experiment, constructed a multiple period DID model, and empirically tested the impact and mechanism of the accelerated depreciation policy of fixed assets on the level of R&D innovation of enterprises. The study found that the accelerated depreciation policy of fixed assets can significantly promote enterprises to improve the level of R&D innovation. The heterogeneity analysis showed that in terms of the impact on the level of R&D innovation of enterprises, the policy has a better incentive effect on the level of R&D innovation of enterprises in low marketization areas and mature enterprises. From the perspective of the impact mechanism, the policy mainly improves the level of R&D innovation by promoting enterprises to increase R&D investment and increase fixed asset investment. This paper will be helpful to understand the logical mechanism of the relationship between accelerated depreciation policy of fixed assets and R&D innovation level of enterprises, and it will provide empirical evidence for improving tax incentive policy and promoting economic transformation and upgrading, which has important theoretical and practical value.

Key words: tax incentive, accelerated depreciation policy of fixed assets, R&D innovation, multiple-period DID model