In infrared optical adjustment system,the lens distance is an important parameter that needs to be precisely controlled.Since the mirror is usually used in infrared optics as a folding path,traditional decoration methods cannot be directly applied,so the high precision optical system has been focusing on the adjustment method at mid distance from folding path.In this paper,two methods of mounting for folding the optical path namely contact type adjustment and non contact adjustment are proposed.The two adjustment methods are verified using small aperture mirrors.The results of the two methods are compared,and the advantages and disadvantages of the two installation and adjustment methods are analyzed.