The invention discloses a method and device for completing movement of double slotted flaps by using one actuating cylinder under a thin airfoil profile. According to the method and the device, by means of additionally arranging a connecting rod at the front end of a telescopic rod of a flap actuating cylinder, the maximum extension length of the telescopic rod of the flap actuating cylinder can be shortened, and meanwhile, the maximum deflection angle of the flap actuating cylinder can be shortened; the stretching and deflecting ranges of the flap actuating cylinder are controlled to be always located in a section profile range of an airfoil, so that a bulge which is arranged on a bottom airfoil surface of the airfoil to dodge the flap actuating cylinder is cancelled, and thus, the aerodynamic characteristics and strength of the airfoil are improved. According to the method and the device, a single-input double-output control mode is realized structurally; in a relatively small airfoil profile space, one telescoping driving input action is realized, and two output modes for two output actions, namely the translation and rotation of a main flap and the rotation of a sub-flap, are completed.