This paper is to investigate the post-derailment dynamic behavior of the half car and to verify the proposed post-derailment dynamic model. Firstly, a half-car derailment experiment is conducted in the laboratory. Then a comprehensive post-derailment dynamic model of half-car is put forward. The model is composed of three parts, namely, dynamic model of half-car, collision detection model and the contact force model, respectively. In addition, the kinematic analysis is carried out to investigate the possible path of motion after derailment. Through the comparison analysis of laboratory test and numerical simulation, the post-derailment dynamic model of half-car is validated, and can reflect the dynamic behavior after the derailment. Accordingly, the collision detection model and contact force model adopted in the post-derailment dynamic model of half-car can be used in the post-derailment simulation to detect the contact conditions and calculate the contact forces.