Abstract: Taking the Yangtze River Delta as a research area, this paper investigated the spatial effect and influencing mechanism of digital finance on high-quality development from the theoretical and empirical aspects. The findings were as follows: (1) Digital finance could promote the high-quality development of local and neighboring areas, and there were characteristics of dimensional heterogeneity, temporal heterogeneity and spatial heterogeneity. In terms of dimensional heterogeneity, the coverage breadth and use depth of digital finance had a significantly positive effect on local and neighboring high-quality development, while the digitalization degree had a significantly negative effect on local and neighboring high-quality development. In terms of temporal heterogeneity, the long-term impact of digital finance on local and neighboring high-quality development was greater than the short-term impact, indicating that the network effect and “Metcalfe’s law” of digital finance were significantly established in high-quality development system. In terms of spatial heterogeneity, the spatial spillover effect of digital finance and its subdivision dimension gradually decreased with the increase of geographical distance, and 215 km was found to be the effective spillover boundary. (2) The collaborative agglomeration of manufacturing and producer services (hereinafter referred to as “industrial collaborative agglomeration”), local government behavior (official replacement, fiscal expenditure bias, environmental regulation) were the important ways for digital finance to affect high-quality development, and could form collaborative forces with digital finance construction. (3) In the low-value region of high-quality development and the high-value region of Internet development, the dividend release of digital finance on high-quality development was more obvious.