The excellent insulation performance of roof insulators is crucial to the reliability of operating trains. The complex environment encountered by trains may cause roof insulator insulation failure, thus affecting the normal operation of the train. The field operation experience shows that during the operation of Hainan CRHAF-A trains, partial arcs are generated frequently on the roof insulators and even flashover accidents occur. In addition, the insulation failure probability of the insulators in the coastal environment is higher than that in other areas, and pollution is an important factor leading to lower insulation performance. Therefore, the pollution accumulation characteristics of roof insulators are investigated and analyzed in this paper. The accumulated pollution simulation model is built based on the operating environment of the train, and the electric field, flow field, and pressure field around the roof insulators are simulated. This has important engineering application and economic value for the study of insulator anti-pollution.