In the context of anti-globalization and increasingly fierce technological competition among countries, exploring the impact of U.S. additional tariffs on Chinese enterprise innovation holds significant research value and policy implications. Based on an international trade model incorporating financial frictions and enterprises’ endogenous R&D decisions, this paper identifies two key channels through which U.S. additional tariffs affect enterprise innovation: market size and financing constraints. Using a merged dataset comprising publicly listed companies, customs records, and tariff data, this paper employs a DID model to conduct an empirical analysis, leveraging the quasi-natural experiment of U.S. additional tariffs at the firm level. The empirical results indicate that: First, U.S. additional tariffs significantly reduce both innovation input and output among Chinese enterprises. Second, the negative effect of additional tariffs is primarily borne by high-tech enterprises and those with higher industry-specific irreversible investments, while regionally targeted policies can effectively mitigate the adverse impact of U.S. additional tariffs on enterprise innovation. Third, in terms of mechanisms, the impact of additional tariffs operates mainly through market size effects and financing constraints, confirming the hypotheses proposed by the theoretical model.

This paper has the following contributions: First, by taking U.S. additional tariffs as a quasi-natural experiment and precisely identifying the treatment enterprises based on firm-level import and export tariff calculations, it provides a valuable supplement to the existing literature on trade frictions. Second, within the framework of an open economy, it constructs an international trade model incorporating financial frictions and enterprises’ endogenous R&D decisions, integrating market size and financing constraints into a unified analytical framework, which reveals their interactive effects in reducing R&D investment under intensified trade frictions. The empirical analysis, based on firm-level microdata, further validates the theoretical hypotheses, expanding the scope of research on the determinants of enterprise innovation and offering new empirical evidence on the micro-level mechanisms through which trade frictions affect innovation dynamics. Third, the findings underscore that the synergy between national macroeconomic policies and enterprise innovation can effectively mitigate the adverse shocks of the complex international environment, counteract the risks of economic decoupling and supply chain disruptions, and promote deep industrial transformation and upgrading.