Abstract: To improve the stability of prefabricated buildings, experimental research on the mechanical properties of welded steel bar trusses in steel structure prefabricated buildings is designed. Firstly, establish a beam column model for prefabricated steel structures. Then, specimens of D5, D6, and D8 types of truss materials were prepared. Finally, place the 1-6 steel bar test blocks into the press for testing, and record the real-time readings and deformation of the steel bar test blocks during the testing process. The simulation experiment results show that under the condition of equal height in prefabricated buildings, buildings with D8 steel structure steel bars as trusses have stronger stability and compression resistance, indicating that in large-span construction, the higher the mechanical performance level of welded steel bar truss structures, the stronger the stability ability of prefabricated buildings.