Abstract: Marginal areas refer to regions that are far from regional development centers, affected by natural conditions or acquired factors, resulting in low population density, insufficient development factors, and a relatively backward comprehensive development status. They are key difficult areas for promoting common prosperity and realizing integrated urban-rural development. Against the backdrop of the high-quality development and construction of Zhejiang Province as a demonstration zone for common prosperity, and the promotion of clustered development of small towns, this study takes the 'Three Cross-City Towns' in Hangzhou-Jinhua-Quzhou as the research object, explores four development models for the collaborative development of small towns, and proposes five collaborative paths covering industry, mechanism, factors, space, and facilities. The purpose is to summarize the practical experience of cross-regional collaborative development of small towns in marginal areas and provide references for the development of small towns in the vast number of marginal areas in China.