In order to realize the alignment of primary and secondary mirrors in large aperture telescopic system and improve optical imaging quality, a new method for adjusting comparative position and pose between primary and secondary mirrors is introduced named high-precision alignment machining. Other than a traditional method of adjusting washer, the method can eliminate astigmatism aroused from inclination between primary and secondary mirrors, and coma aberration aroused from secondary mirror′s eccentricity at the same time. The method reduces the alignment difficulty markedly and avoids systemic instability. In addition, a new method for primary and secondary mirrors test is established by combination of interference auto-collimating tests and cross wire application which replaces optical axis. The alignment and test′s result from the Φ520 mm primary and secondary mirrors shows that root-mean-square (RMS) value of wave aberration hardly changes before and after assembling, and is entirely less than 0.03λ (λ=632.8 nm), axial angles swaying in primary and secondary mirrors are 0.72″ and 2″, respectively, the verticalities of two mirrors optical axis and respective frames are less than 0.005 mm, primary and secondary mirrors′s concentricity is less than 0.01 mm, and the RMS value of the system is less than 0.7λ after interation, which achieves design requirements.