Aiming at the concave aspheric mirror with large aperture or large relative aperture, catadioptric null compensating test is proposed. To carry out the null compensation test of concave aspheric surface, double lens and single mirror are used. The catadioptric compensator is set in front of curvature center of tested mirror. Based on third-order aberration theory, making spherical aberration coefficient S1=0, the calculating formulas of initial configuration structure parameters are derivated. This novel testing method is studied by design of catadioptirc compensators for the following three situations, the design results and drawings are given: 1) mirrors(F/2, e2=1.05) with different apertures; 2) mirrors(Φ0=2000mm, e2=1.05) with different relative apertures; 3) to design catadioptric compensators for mirror (Φ0=2000mm, e2=1.05, r0=8000mm) with different inner obscuration ratio. The analysis shows that this new method is available to test concave aspheric mirror with large aperture or large relative aperture.