The high lifting device is a set of movable panel on the wing to improve the air flow and increase the lifting force. It can increase the curvature and effective angle of attack of the wing section when the aircraft takes off, lands and maneuvers at low speed. Therefore, it has a decisive influence on improving the lowspeed performance for large civil aircraft, including the approach attitude. In the lowspeed takeoff and landing, it is generally required to reduce the flight speed and the taxiing distance as much as possible, and at the same time to achieve a higher lift coefficient, which means that the lifting device also has a large deflection at this time, and the load acting on it will be relatively large. Therefore, the load calculation of high lifting device for the large transport aircraft is one of the key tasks in its design, which is of great significance in the load design process for civil aircraft. This paper mainly introduces the calculation principle and design method of the lifting device load for the civil aircraft, and gives a set of engineering algorithm for the aerodynamic and inertial loads of the flap slat.