Abstract: Improving the intelligent level of centralized control of urban building power system is an important way to realize low carbon building and energy saving. The combination of comfort and energy saving is of great significance for energy saving optimization of urban building because comfort is an important function of urban building. The energy consumption composition of three kinds of power consumption system of urban building including air conditioning, lighting and elevator is analyzed, and the corresponding power consumption index is proposed. The connotation of urban building comfort is studied in this paper. The comfort degree uncertainty brought by the change of season, weather, temperature and traffic flow is studied. On this basis, thermal comfort, light comfort and elevator comfort index are established. Energy saving optimization model with uncertain factors is put forward not to reduce the consumers' comfort. The optimization model is proposed to minimize the total energy consumption and satisfy the chance constraints of the given confidence level with the comfort degree. The improved PSO algorithm is applied to solve the optimization model. The validity of the urban building energy saving optimization model based on comfort and the optimization algorithm is verified through the case study.