Abstract: Multi-body dynamics modeling and simulation has also become an important means to study the dynamic performance of the tracked vehicles, where the reliability of the analysis results depends on the accuracy of the established dynamics model. In this paper, a self-developed small mountain crawler chassis was used as the research object. To ensure the accuracy of the dynamics model, the centroid coordinates and Euler angles of the crawler chassis were selected as generalized coordinates. And the kinematics equation of the crawler chassis was established by using the limit theory and the transient motion analysis method, and the dynamic equation was established by the Lagrangian method, where the parameters that affected the precision of numerical simulation model in theory was analyzed. On this basis, combined with the topology analysis, the multi-body dynamics model of the crawler chassis was established. Firstly, using the three-dimensional software SolidWorks, combined with the physical prototype and design drawings of the crawler chassis, the three-dimensional model of the components was built and the quality characteristics, such as the coordinates of centroid, mass, moment of inertia and so on, were calculated. Secondly, the three-dimensional model of the components was imported into the multi-body dynamics software RecurDyn, and the parametric modeling of the tracks, drive wheels, tensioners and other wheel train components was built in a RecurDyn/Track (LM) environment. All of these were assembled to establish a preliminary multi-body dynamics model of the crawler chassis. Thirdly, combined with the topology analysis of the crawler chassis, the constraint relationship among the components was defined. And the quality characteristic parameters of each component were defined according to the previous calculation results. Finally, according to the actual vehicle test results under the idling condition of the crawler chassis, the stiffness coefficient and damping of the internal bushing force of the crawler belt were determined by the trial and error method. The coefficient was debugged, and the pre-tensioning force of the crawler belt was in accordance with that of the physical prototype measured at rest. In order to further verify the reliability of the established multi-body dynamics model of the crawler chassis, the real vehicle test of the crawler chassis were carried out, where two straight running conditions on hard ground and soft terrain were taken into account, and the parameters such as the average speed, side position offset, driving wheel torque and tension force were considered. By comparing the results between real vehicle test and simulation analysis under the two working conditions on hard ground and soft terrain, the validity and credibility of the model were verified. The results showed that the simulated analysis data and the actual vehicle test results of the average speed, side position offset, driving wheel torque and tension force of the crawler chassis under rigid and soft road conditions were in good agreement. The error was 5.00% and 2.27%, 3.86% and 6.83%, 3.15% and 4.66%, 0.15% and 0.62%, respectively, and the range between the simulation and the measured of driving wheel torque and tension force were 3.05% and 7.30%, 2.80% and 4.02%, respectively. Therefore, the established dynamic model of crawler chassis had high accuracy and good consistency of fluctuations, which could provide a reference model for the in-depth study of the dynamic performance of the crawler chassis.