The invention discloses a method for correcting feedback of an inertial navigation system/global position system (INS/GPS) combined navigation system based on lever arm estimation. The method comprises the following steps of: extending a lever arm error to a system error state vector for estimation, judging whether a random error of an inertial device is accurately estimated through comparing whether the difference between a lever arm estimation value and a true value exists in an error threshold range, wherein the error of the inertial device is effectively estimated when the error of the lever arm estimation value is smaller than a set threshold value, measured outputs of a gyroscope and an accelerometer are corrected by utilizing the error of a random constant of the estimated inertial device, and unity feedback correction is performed during combined Kalman filtering, otherwise, feedback correction is not carried out on the error of the inertial device. According to the method, the error of the random constant of the inertial device can be subjected to effective estimation and unity feedback correction, and the precision of the INS/GPS combined navigation system can be effectively improved.