Since maglev vehicles run at a very high speed of 500km/h, many aerodynamic problems arise, such as aerodynamic drag and vibration of car. In order to reduce these aerodynamic effects, field tests, wind tunnel tests and numerical simulation have been performed. In these studies, this paper mainly presents the results of visual studies of the flow around the vehicles and aerodynamic brakes operated on the Yamanashi test line which were performed by numerical simulation and the surface tuft and the mist methods. The simulation results are compared with measured results in the field tests. A comparison shows that simulation is an effective tool to investigate these problems.