Abstract: Based on the SST k-\omega turbulence model and the IDDES method, a three-dimensional numerical model was used to simulate the transient state of an evacuated tube maglev transport system at 800 km/h in the choked (blockage ratio of 0.3 and 0.2) and unchoked (blockage ratio of 0.1) states. The accuracy of the numerical method was verified using transonic wind tunnel bump test data. Additionally, the significant coherent structure of the flow field was extracted based on the proper orthogonal decomposition, the region with the strong unsteady load on the train surface was identified, and its space-time evolution law was revealed. The results show that the load distribution on the upper surface of the train is similar to that of the Laval nozzle, and the difference in load distribution between the chocked/unchoked conditions is mainly in the divergent section. The load distribution on the lower surface of the train becomes complex due to the abrupt change in the cross-section of the bogie cavity. The difference in the interaction between the upwash and downwash flow leads to different locations of the temperature peaks under the choked/unchoked conditions. The strong unsteady pressure region on the train surface is mainly located at the bottom bogie and has a characteristic frequency of 14 Hz. The tail car shock wave is also an unsteady source under choked conditions. The first-order modes of the middle and tail car temperature loads reflect the heat accumulation process.