In order to improve the overall performance of the brake system of urban rail vehicles, the theoretical analysis and ground test were adopted to verify the effect of the internal friction force of the brake unit of the urban rail vehicles in the process of braking and remission. The actual output of shoe pressure was proved different under the same brake cylinder pressure. The effect of the characteristics on the overall performance of brake system, such as common brake performance and brake shoe wear, was proposed, and the corresponding measures were put forward, which would provide reference for the scheme design of the braking system of urban rail transit vehicles in the future.