To satisfy the comfortable demand for passengers during peak period in a low service level, the on-bus service level is divided into four grades with a standard of standing-passenger density based on the theory of computer visual simulation. An improved on-bus perceived value model of different service is proposed with the introduction of passengers' income, and the average of perceived value for different service level under different income of passengers is obtained. Furthermore, the model of departure interval considering passengers' perceived cost is formulated. The model was applied to the 649 bus route in Tianjin City, and the optimal departure time in peak period is derived based on MATLAB. Results show that it is necessary to consider passenger's perceived cost when the on-bus perceived value is 38%-69% in total during peak period. Passenger's perceived cost is cut down sharply while bus company basic interests be guaranteed. It reflects people-based service concept and may provide important scientific support with promoting the attraction of bus systems.