Abstract: Trolleybus is a new and green urban public transportation means that integrates the advantages of road transportation and rail transportation. The brake system is extremely important as the core system to ensure its safe operation and reliable parking. In order to quickly analyze the characteristics of the air circuit and verify the design logic of the brake system, the braking characteristic analysis method based on virtual test was proposed. Taking the brake system of a 3-group 6-axle trolleybus as the research object, the composition principle and key parameters of the brake system were clarified, and the digital model of the brake system based on the theory of gas dynamics was established. The virtual test of the brake cylinder pressure characteristics under two braking modes and different master control were carried out. The research results show that the virtual test based on the digital model of the brake system can quickly verify the design logic of the brake system and obtain the characteristics of the air circuit. When 1 and 3 cars are under master control, the brake cylinder pressure of the traveling brake of 1 and 3 cars is 0.83 times of the average value of the brake cylinder pressure of the remaining two cars, and the braking response time is in line with the design requirements. The research results provide support for the braking performance analysis and parameter optimization design of trolleybus.