The transient pressure waves and pneumatic force of high-speed trains passing each other in the open air will adversely affect the safety of train operation. Using the numerical method of three-dimensional, unsteady, compressible fluid control equation and two-equation turbulence model unsteady, compressible fluid control equation and two-equation turbulence model, the pressure changed for 300km/h high-speed rains passing each other in the open air based on overset mesh. The results show that the method of overset mesh can solve the problem of the pressure wave changed for the high-speed trains passing each other, and the grid transmission accurate between master zone and salve zone. There are 70m away from the high-speed trains, when the high-speed trains start rendezvous in 0.42s, the pressure wave “head waves” of front nose is appearing, the pressure of the front nose is maximum. The front of the train traveling through the rear of the train in 0.95s, two cars vertical coincidence, making a “trail wave”.