In order to ensure the safe and efficient construction of large-span cantilevered steel structures, it is of vital importance to study their key construction technologies and process control methods. This article takes the eye prevention and treatment center building of an industrial park project as the engineering background, its cantilever section is in the form of a steel truss structure, with a maximum overhanging length of 25.3 m. This cantilevered steel structure is the key sub-project with the highest technical difficulty and the greatest safety risk in this project. To solve the difficulty of installation, through construction scheme comparison and selection. Meanwhile, numerical simulation of the construction process is carried out by using the finite element software ABAQUS to solve the problems of deflection control and temporary support during the installation of steel structures, ensuring the installation quality and construction safety of large-span cantilever steel structures. Research shows that: 1) Project success hinges on proper disassembly sequencing and temporary support design; 2) Numerical analysis is key to addressing related challenges, supporting on structural slabs can induce punching shear, necessitating local reinforcement such as additional propping from below.