Urban agglomeration policy, essential for high-quality regional development, creates new opportunities for urban-rural integration. From the perspective of factor mobility, this paper uses panel data for 280 cities at or above the prefecture level in China from 2003 to 2023, focusing on the implementation of 18 urban agglomeration policies, and constructs an evaluation framework for urban-rural integration development across five dimensions: population, economy, society, space, and ecology. A multi-period DID model identifies the effects and mechanisms of urban agglomeration policies on urban-rural integration. The findings reveal that urban agglomeration policies facilitate integrated urban-rural development, primarily by promoting the flow of labor, capital, technology, and data factors. The effects are more pronounced in cities located in central and western regions, non-resource-based cities, smart cities, and non-national-level urban agglomerations. Based on these findings, strengthening regional collaborative governance mechanisms, deepening market-oriented reforms of factors, and implementing function-driven differentiated development strategies will inject strong momentum into advancing integrated urban-rural development.