Abstract: This study approaches from the perspective of the sharing economy, systematically examining the governance effect of shared electric bicycles as a new energy travel mode on urban air pollution and its mechanisms. The research finds that after the introduction of shared electric bicycles, the level of urban air pollution decreases, and the environmental benefits exhibit a sustained enhancement year by year. Mechanism tests indicate that this environmental protection effect arises from the reduction of exhaust emissions due to the substitution of motor vehicle travel, which forms a network synergy effect with rail transit connectivity. Heterogeneity analysis reveals that relaxed entry policies can improve the emission reduction effect, national brands have better reduction effects compared to local brands, and cities with higher levels of digital economy development show more significant reduction effects, reflecting the triple role of institutional environment, economies of scale, and technological empowerment. This paper enriches the micro-evidence of externalities in the sharing economy and not only provides recommendations for the operation of shared electric bicycle brands but also offers empirical support for the government in optimizing access policies for shared electric bicycles, brand choices, and urban traffic structure transformation.