An effective assembly method is presented for 1.3m aperture coaxial quad-inverse lens. The primary mirror has a diameter of 1.3m and is supported by a back bipod. The precise positioning of the supporting structure is carried out by using the laser tracker polygon measurement method, and the position of the primary mirror are adjusted by using the Stewart mechanism position inverse solution method. Surface measurement is made by changing the orientation of the reflector assembly to extract the surface error of the reflector caused by gravity. The optical datum of the reflector and the lens datum can be transferred by centering the reflector based on interferometry using the Offner zero-position compensation detecting light path. The lens is mounted vertically, and the assembly accuracy and convergence speed are improved by testing the lens image height and calibrating the standard mirror shape online. The center and edge field wavefronts RMS of the lens are 0.053λ (λ=0.6328um) and 0.077λ, respectively.