<p>This study relies on panel data from 2008 to 2023 for 3102 Chinese A-share listed firms. It applies a multi-period difference-in-differences framework to examine the policy effects of “Low-Carbon City Pilot Policy” and “Innovative City Pilot Policy” on corporate carbon emission performance, as well as the synergistic effects of both policies being implemented concurrently. The synergistic effects of both policies outperformed their individual effects. This approach compensates for the shortcomings and deficiencies of single policies, enhances their effectiveness, and significantly improves corporate carbon emission performance. These findings remained robust across multiple robustness tests. Mechanism analysis revealed that the coordinated policies improve corporate carbon emission performance by enhancing green investment, increasing innovation quantity and quality. Furthermore, marketization level and digital transformation positively moderated these policy effects. Heterogeneity analysis showed that enterprises in resource-based cities, as well as high-pollution and non-high-tech enterprises, have greater benefits. This study identifies the rebound effect of innovation on carbon reduction and the guiding role of environmental regulations, deepening our theoretical understanding of the relationship between low-carbon innovation policies and corporate carbon emission performance. It also provides empirical evidence and practical insights for low-carbon economic development and sustainable policy design.</p>