Abstract: Analyzing the temporal and spatial characteristics of the vitality distribution of ancient tourism towns and clarifying the driving factors of their built environment are of great significance to promoting the spatial quality of ancient tourism towns and their balanced development. Taking the ancient town of Dayan in Lijiang City as an example, Tencent location big data is used to characterize the spatial vitality distribution of the ancient town during the day and night, and the global Moran's I index and the local correlation index (Getis-Ord GI^*) are used to reveal the temporal and spatial distribution of its vitality, and using geographic detectors to clarify the driving factors of its built environment, the results show that:(1) The day and night vitality distribution of Dayan Ancient Town has obvious spatial heterogeneity. Daytime crowd activities show the spatial distribution characteristics of ‘multicore spreading’ in hot spots and ‘cluster gathering’ in cold spots, and night crowd activities in hot spots show an obvious ‘core-sub-core’ multilayer polar core structure. (2) There are obvious differences in the influence of spatial accessibility, functional facilities and material interfaces on the day and night vitality distribution of Dayan Ancient Town. Among them, the daytime vitality of ancient towns is greatly affected by proximity (r=n), overall functional density and building density; nighttime vitality is more affected by the density of leisure facilities, proximity (r=400m) and building density. (3) The interaction of various driving factors has a positive effect of double-factor enhancement or non-linear enhancement on day and night vitality of Dayan Ancient Town.