Abstract: According to characteristics of out-of-gauge goods wagons, SIMPACK simulation software was utilized to establish two dynamics models for single-vehicle NX_70H flat and NX₇₀ flat. Based on the models, roll angles, yaw angles, lateral offsets and lateral vibration offsets were obtained under the speed of 20~120 km/h onⅠ-level line and the speed of 20~70 km/h on Ⅲ-level line. Simulation results indicates that the speed and road conditions have a great impact on the characteristics above, and the values of lateral vibration offset in both models simulated on Ⅲ-level line are all greater than those on Ⅰ-level line. The least favorable condition occurs when the two models are running on Ⅲ-level line or at high speed on Ⅰ-level line. The lateral vibration offsets are larger at the hind part of the vehicle, and calculated points above 3 600 mm distancing the rail surface are the least favorable points. The results play a remarkable role on the real vehicle field test.