Aiming at the certain A1A-A1A (power with four driving equipments mounted in the frame of six axles) DMUs, dynamic model of the motor vehicle was established with multi-rigid-body dynamics software SIMPACK, and a simulation analysis of the motor vehicle dynamically negotiating the 300 m radius curve was done, which was compared with the measured result. The results showed that: the dynamic performance of the motor vehicle was both affected by the local and random irregularity with the later accounting for 60%, and at the same time, the value of the random irregularity at the transition point was larger than that on the circle in the actual line. In practice, the transverse irregularity of the 300 m radius curve at the transition point was close to that of the poor line, while on curve it’s slightly larger than that of the AAR5 level. The vertical irregularity at the transition point was very close to the AAR5 level, and the AAR6 level vertical irregularity could represent that on the curve; The maximum value of the measured derailment coefficient was about 1.2 times than that of the poor line, while the average maximum was 1.1 times than that of the poor line. Therefore, the difference of irregularity should be considered in future simulation analysis.