The rotational resistance coefficient of the bogie is a critical parameter for assessing the operational safety of vehicles, significantly influencing the stability of the vehicle’s snaking motion and the safety of curve negotiation. This paper conducts measurements of the rotational resistance coefficient using a 6- degree-of-freedom bogie test rig, evaluating the variation patterns of the indicator under different vehicle load conditions and air spring inflation states. By establishing a SIMPACK dynamic model of the 6-DOF platform, it is possible to obtain actuator displacement control curves that comply with the EN 14363 standard. Taking a specific subway trailer bogie as an example, the rotational resistance coefficient under various operating conditions was measured. The test results indicate that under the condition of air spring deflation, the rotational resistance coefficient is significantly higher than that under air spring inflation. Moreover, under the condition of air spring deflation, the effect of vehicle load on the rotational resistance coefficient is negligible. Due to assembly errors and the approximate methods used in calculations, the hysteresis curve of the rotational resistance torque-angle measured by the 6-DOF test rig exhibits minor fluctuations, which have a minimal impact on the results, and there is room for further optimization. The method proposed in this paper can provide a basis for vehicle design optimization, reduce the risk of derailment, and also assist in vehicle maintenance and repair during the operation stage to ensure safe operation. It has been widely applied in the design and operation practice of subway vehicles.