Abstract: To get the load-bearing behaviors and design methods of a modularized prefabricated steel structure with lean-brace joints,the finite element analysis method was adopted,the restraints effect of the whole structure of the lean-brace column was considered,the load-bearing capacity of lean-brace column was studied in the integral structure,the calculated length coefficient of the column was conversely derived by the ultimate load-bearing capacity,which solved the key problem in design of the structure system.The integral finite element analysis of a 30-layer structure was performed,the loadbearing capacity,the failure mode and failure mechanism of the new-type structure under overload horizontal load,overload vertical load and overload were obtained.The failure mode of the system was in accordance with the seismic principle of “strong column weak beam”.Analysis shows that the structure has better lateral stiffness,but poorer ductility.It is reasonable to control the ultimate load-bearing capacity coefficient to 2.0 under horizontal load and vertical load,which has enough safety margin.