According to the requirement of long focal length and compact optical system for airborne platform, a catadioptric system with long focal length and high resolution is designed by using an improved R-C mirrors and a spherical correction lens to correct spherical aberration, coma and chromatic aberration in full field. This system has a focal length of 1 500 mm and field of 2°. The envelopment diameter of the optical system is no more than φ400 mm, the Modulation Transfer Function is better than 0.56 @62.5 lp/mm, and the imaging quality is approaching to diffraction limit. In order to improve efficiency and reduce the difficulty of alignment, the imaging quality of the central and adjacent field of the R-C primary and secondary mirror is controlled to diffraction limit. The sensitivity matrix of the mapping relationship between the misalignment and primary aberration is established by means of interferometer detection and computer-aided alignment. The aberration characteristics of the misalignment optical system are analyzed. The optical precise alignment scheme of wavefront accurate measurement and inversion of the misalignment is proposed. After alignment, the RMS value of the whole system is better than 1/13λ, achieving the imaging quality requirements.