Abstract: To understand the influence of different coupler buffer devices on the safety and comfort of the operation of heavy haul train, and study the dynamic characteristics of coupler buffer device of heavy haul trains. In this paper, the dynamic longitudinal dynamics model of the train operation process and the coupler and draft gears model were established based on the train operation data of the Daqin Railway and the actual operating environment of the train. According to the models, the dynamic characteristics of trains equipped with QKX100 and MT-2 buffers operating on the Daqin Line were studied. The simulation results show the longitudinal dynamic model of train, the model of coupler and draft gears are close to the experimental results of many institutions at home and abroad, which demonstrates the accuracy of the train operation model established in this paper. Contrast simulations of heavy haul train with two kinds of buffers on Daqin line in terms of emergency braking, cyclic braking and traction operations were carried out. Results show that the maximum coupler force and maximum acceleration of the train equipped with the QKX100 buffer are smaller, far lower than the prescribed safety limit, and the safety and comfort of the train are greatly improved.