A method for installing an ultra-high-temperature, ultra-high-pressure gas boiler and its auxiliary equipment, comprising the following installation steps: boiler foundation marking, boiler steel frame installation, drum installation, air preheater installation, economizer installation, water wall combination, front Water-cooled wall installation, right water-cooled wall installation, rear water-cooled wall installation, left water-cooled wall installation, wall-wrapping team, wall-wrapping installation, superheater installation, reheater installation, body pipeline installation, guard plate furnace wall installation, its features That is, the installation of the boiler steel frame is the installation of separate parts, and the boiler steel frame is a three-dimensional frame structure. The steel frame is divided into different sub-package parts through the uprights and then assembled and installed as a whole. The beneficial effects of the present invention: reduce high-altitude operations, Protect the life and property safety of the staff, improve work efficiency, reduce working hours, shorten the construction period, the installation accuracy can be controlled at any time, improve the accuracy of the sub-assembly parts of the steel frame, improve the assembly accuracy after the steel frame is assembled, and ensure the follow-up installation of boilers, etc. installation accuracy.