In recent years, with the rapid development of the aerospace industry, precise airdrop and recovery system have gradually received more widespread attention. Due to the main working environment of the parafoil in the troposphere, the air flow situation is relatively complex. Therefore, it is necessary to study the aerodynamic performance of parafoil in complex flow field environment. In this paper, the incoming flow is decomposed into two factors: speed and direction, and the influence of continuous change of incoming flow direction on the aerodynamic performance of parafoil is mainly considered. Using the method of computational fluid dynamics, the finite volume method is used to discretize the Reynolds time-averaged stress equation. In this paper, the spatial discretization of 16 m2 parafoil is carried out by overset grid. The aerodynamic performance of parafoil is solved when the incoming flow direction changes 100°, 10°and 1° per second, and compared with the results of steady calculation. The results show that with the increasing of the change rate of the incoming flow direction, the lift and drag coefficient of the parafoil will gradually increase, reaching the maximum at 100°per second. When the rate of change of direction is 10°/s and 1°/s, the lift and drag coefficient are almost the same as those in the steady state. When the rate of change of direction reaches 100°per second, the lift coefficient and drag coefficient increase significantly. It can be proved that when the direction of the incoming flow changes slowly, the aerodynamic performance of the parafoil gliding will not be affected in any way.