The full-aperture surface measurement of the secondary mirror was always a difficult problem in interferometric testing. In order to realize the full-aperture testing of coaxial high-order SiC aspherical mirror, a null compensation measurement model based on CGH was proposed. With this model, the null compensation testing for a 90 mm aperture high-order SiC aspherical mirror was designed. By calibrating the influence of the transmission wave aberration of CGH in the test results and removing it in the secondary mirror test results, the accurate CGH null compensation testing of the high-order SiC aspherical secondary mirror could be effectively realized. This method could provide technical support for the high-precision manufacturing of aspherical secondary mirror in aerospace.In order to realize the CGH compensation design of the high-order SiC aspherical secondary mirror, combined with the engineering example, the CGH null compensation design of the interferometer plane wave incident was carried out on a high-order SiC aspheric secondary mirror with an aperture of 90 mm, a vertex curvature radius of 422.6 mm, a quadratic term coefficient of 9.1, an aspheric high-order term A4 coefficient of 3.92, and an A6 coefficient of 4.72. The design of the optical path was shown in Fig.2. In order to accurately realize the high-precision alignment of the interferometer, CGH and the SiC aspherical secondary mirror to be tested, the interferometer and CGH alignment area on the CGH were designed at the same time, as shown in the blue area in Fig.2. It formed dry fringes with the reflected light of the standard lens in the interferometer through reflection diffraction. By adjusting the position of the CGH, the fringes became zero fringes. At this time, the interferometer and the CGH were strictly aligned. The green area in Fig.2 was the aspherical secondary mirror testing area, which finally completed the surface map measurement of the convex aspherical mirror.From the design analysis of this paper, it could be concluded that based on the secondary mirror compensation design method in this paper, the RMS value of the theoretical design accuracy of the compensation design was 0 nm, which verified the accuracy of the design method in this paper. At the same time, the interference testing and error analysis on the secondary mirror were carried out. The RMS value of the full-aperture surface testing result reached 0.015λ (λ=632.8 nm) (Fig.8) and the relative RMS value was 0.016λ (λ=632.8 nm) (Fig.11) after calibration, which further verified the reliability of the proposed method.In this paper, a design method of null compensation CGH for high-order SiC aspherical secondary mirror was proposed. In order to achieve a more accurate full-aperture measurement of the secondary mirror surface map, the transmission wave aberration effect of CGH was calibrated in the test results and removed in the secondary mirror test results. According to the CGH design method of high-order aspheric secondary mirror and the experimental results in the testing, it could be seen that the design method described in this paper could effectively realized the CGH null compensation design of high-order aspheric secondary mirror. At the same time, according to the error analysis results, this paper effectively calibrated the influence of CGH transmission wave aberration on the secondary mirror interference testing results, which could provide technical support for the high-precision manufacturing of aspherical secondary mirrors.