The N-S equations were solved by numerical simulation to study the aerodynamic characteristics of grid wings. The flow field of tactical missiles with grid wings and planar wings at high angle of attack was calculated and main focus was performed on the influence of geometry characteristic size to aerodynamic characteristics of grid wings. The result indicates that grid wings have advantages of large stall angles and small hinge moment to planar wings. The axial force is significantly affected by grid numbers, web thickness and cross-section shapes, but the wing normal force is less affected.