In image-aided terminal inertial guidance system geometric distortion is induced in missile-borne image with varying missile attitude.The affine projection maintains the parallel structure of the objects，on which a method of geometric distortion correction of missile-borne image is proposed，and the affine projection is applied to the terminal corrected images. The function of the perspective target and its affine projection with the missile pitch is deduced based on the perspective geometry character of the missile-borne camera. That is used to achieve the terminal corrected image using the integrated information of the inertial navigation system (INS) and image by setting appropriate reference frames of the two systems. The results of simulation demonstrate that the method proposed is feasible to correct the geometric distortion induced by the missile attitude and increase the object position accuracy. Furthermore，the method is not sensitive to the INS error and consumes little time.