The invention discloses a method for passivating the aberration of a conformal optical system based on wavefront coding. The method includes the following steps that: an odd-symmetry phase mask plate is additionally installed at the diaphragm of the conformal optical system; the wavefront of the optical system is modulated; a coded image is formed on a detector; and image decoding processing is performed on the coded image by means of a digital filtering means, so that a final clear image can be obtained. Since a wavefront coding technique is introduced, a larger focal depth can be realized with the luminous flux and imaging resolution of the conformal optical system ensured, and astigmatism, spherical aberration, chromatic aberration, and aberration caused by defocusing which is further caused by installation error and temperature change can be suppressed. The method of the invention is simple to operate. With the method adopted, under a condition that the complexity of the conformal optical system is not increased, aberration can be passivated, and image quality can be improved, and therefore, the capture performance and tracking precision of a seeker can be improved.