The wind tunnel tests (in the case of suction plate and normal plate) and numerical simulations of longitudinal aerodynamic force of the 200km/h EMU's traction car are performed, and the longitudinal aerodynamic force coefficients are obtained respectively when the traction car is the front and rear one. The results show that, in the case of suction plate, the aerodynamic drag of the front car and the rear car increase evidently, and the negative lift of the front car increases while the positive lift of the rear decreased; the aerodynamic drag of the sub-floor contributes to the total drag by 25.9 percent. So to decrease drag the emphasis is the sub-floor.