As the next generation of high-speed rail transportation, the high-speed maglev train has a design speed of 600km/h, whose Mach number is about 0.49. The severe aerodynamic effect caused by this high speed has a substantial impact on the train’s stability and safety. In this paper, the aerodynamic moments of two three-carriage maglev trains passing by each other in open air are investigated by numerical simulation. To get transient moments acting on the train, this study adopted the sliding mesh method and the k-ε turbulent model, and a user-defined function was compiled to define the motion of maglev. The results show that the pitching moment is the most important factor for the steady of maglev trains running in the open air. The oscillation of the total aerodynamic moment mainly comes from the moment acting on the lower part. The coupling of the pitching moment acting on the upper and lower part of carriages make the peak of the total pitching moment behind the total yawing moment.