The Maxwell damper model has been adopted in the simulation of railway vehicle dynamics for a long time and became a basic force element in the multi-body dynamics software. The main purpose of this article is to investigate the predictive accuracy of this model for a railway yaw damper in damping characteristics and vehicle stability assessment. To achieve this objective, a simplified physical damper model was developed for comparisons, which is accurate and at the same time presents low computational costs, being able to be adopted in the multi-body dynamics model of a railway vehicle to speed up the numerical simulations. It was suitably validated in the damper rig test, and simulation results for those two damper models were compared with measured data. Results showed that the traditional Maxwell model of this typical yaw damper cannot accurately describe its dynamic behaviors, while the simplified physical model can accurately reproduce the complex behavior of the actual damper system with a high computational efficiency. Comparisons of vehicle dynamics relevant to vehicle stability were then carried out, by integrating the Maxwell model and the simplified physical model presented in this work into a multi-body dynamics model of a high-speed train in China. It was found that the Maxwell model can reproduce the phenomenon of carbody instability accurately if an appropriate value of the dynamic stiffness is set in the Maxwell model. In the simulation of bogie instability, the Maxwell model overestimates the dynamic damping of this typical yaw damper, and as a result it leads to large errors in stability calculations.