Abstract: The development of the new energy vehicle (NEV) industry is a crucial indicator of industrial transformation and upgrading within the context of a low-carbon and circular economy. The ability of the NEV industry to achieve creative transformation and innovative development is closely related to government policy orientation. This paper established a panel threshold regression model, using environmental regulations and tax incentives as threshold variables, to examine the nonlinear relationship between environmental regulations, tax incentives, and innovation efficiency of NEV enterprises. Additionally, a panel regression model was constructed to explore the impact of the policy combination of environmental regulations and tax incentives on the innovation efficiency of NEV enterprises. The study finds that tax incentives have a negative impact on innovation efficiency when the level of tax incentives is below the threshold value, but a positive impact when the level exceeds the threshold value. Similarly, environmental regulations have a positive impact on innovation efficiency when the regulation level is below the threshold value, but a negative impact when the level exceeds the threshold value. Furthermore, the combination of environmental regulations and tax incentives continuously promotes innovation efficiency in a linear positive manner. Based on the empirical analysis results, this paper provides corresponding policy recommendations to further enhance the innovation efficiency of NEV enterprises in China.