Urban haze remains a persistent threat to the ecological environment during city development. To build a Beautiful China, exploring the synergistic haze reduction effects of policy combinations while balancing environmental benefits and economic growth has emerged as a critical objective. Based on city-level panel data from 2006 to 2021, this study employs a multi-period difference-in-differences (DID) approach to evaluate the impact of two national pilot policies—the Smart City initiative and the Emissions Trading System (ETS)—on urban haze. The results indicate that, after undergoing a series of robustness checks, including placebo tests, the combined policy of the Smart City and ETS continues to demonstrate a significant haze reduction effect, with the impact exhibiting a notable time lag. Furthermore, this policy combination achieves haze reduction goals by enhancing energy efficiency and promoting technological innovation, although the pathway through industrial upgrading is not yet evident. Additionally, the haze-reduction effectiveness of the policies is associated with geographic location, administrative level, degree of economic agglomeration, and resource dependency. Specifically, significant haze reduction is observed in central and eastern regions, but not in the western region. Haze reduction effects are more pronounced in non-key cities, cities with low economic agglomeration, and cities with low resource dependency. Therefore, to effectively mitigate haze, it is essential to tailor approaches to local conditions by jointly implementing the Smart City and ETS policies, enhancing energy utilization efficiency and technological innovation capacity, reducing fossil fuel consumption in highly resource-dependent regions, taking into account regional, locational, and resource disparities, fostering tiered urban development, and promoting pilot program experiences.