Train passenger door is the key system for operation and maintenance of urban rail train. In this paper, working process of the passenger door system of urban rail train is analyzed and the mathematical model is established. Firstly, the method of parameter estimation is used to obtain physical parameters of doors in different working conditions. Then fault diagnosis experiment is carried out on train passenger door with principal component analysis and rough set theory. In the end, fault diagnosed accuracies under different time settings of opening and closing profiles with the test rig are verified.