Metropolises in China are undergoing rapid suburbanization processes, resulting in spatial differences in the built environment from the city centre to the outer suburbs. The continuous suburbanization has changed residents’ subjective well-being and behaviours. The association between built environment and subjective well-being has been studied extensively, but there is scarce research on the influence of the built environment on both subjective well-being and behaviours with regards to the self-selection effect in the suburbanization process. This paper constructs an analytical framework to simulate the impacts of the built environment on subjective well-being and behaviours. The propensity score matching method is applied to questionnaire data from Hangzhou in 2018 to investigate these impacts. The results of this research show that in three selected districts, the mean score difference for fitness and social behaviour is quite significant (0.4 and 0.2, respectively), whereas the mean score for subjective well-being is 0.1. Both fitness and social behaviours are significantly and positively related to subjective well-being. Fitness behaviour has a greater impact than social behaviour. The four dimensions of built environment impact on both subjective well-being and behaviours after self-selection were controlled using the propensity score matching method. The results of the study can inform local governments; exurban development zones should be equipped with more high-end public facilities and public transportation in order to improve residents’ quality of life in the suburbanization process.