In order to popularize the prefabrication and installation technology of double-wall pipe,the prefabrication and installation process of gas double-wall pipe with the fixed support used in the 45 000 m3 LNG carrier is described in detail, mainly including the structural characteristics of double-wall pipe, shaping methods and weld welding sequences of several basic double-wall pipes, and procedure characteristics, difficulties, and notes for double-wall pipe to install, make the pressure test, and clean on the ship, which can be used as a reference for the similar project management team and relevant personnel.