The impacts of the built environment on the public health might be difficult to be confirmed, as they are affected by a long exposure time, with various influencing factors, which are hard to be measured. In order to establish an intuitive correlation between the built environment and the public health, this study takes the healthy behavior as the mediator variable. According to the physical and mental health status of elderly people(N=3431) from 115 communities in Shanghai, we take 6 ranges of the built environment factors to construct a mediating effect analysis model with the physical activity and the social activity as the mediator variables. The built environment factors are the density, the design, the housing, the green space, the public facilities and the location. It is found that the physical activity and the social activity are effective mediators, and the mediating effects of the healthy behaviors are shown to more clearly reveal the extent and the direction of the impact of the built environment on the elders' health condition. Based on the practice, the behavioral variables' adjustment directions of the health outcome are similar, but the degree of the adjustment is different among the different neighborhoods. For the high-density human settlement in megacities represented by Shanghai, the optimization of the quality of the built environment for promoting the social activities has a more significant impact on the health of the elderly.

built environment  /  elder adults  /  health behavior  /  mediating effect