Abstract: To get the mechanical characteristics,failure mode and mechanism,the horizontal and vertical loading tests were performed on 4 full-size one-layer and two-span frames.Its mechanical characteristics,load-bearing capacity,deformation characteristics,failure model and mechanics were studied in the paper.The influence regulation of ultimate bearing capacity was obtained by contrasting analysis with frames having different thickness of components and different layout of lean braces.The finite element models of 4 full-size frames were analyzed,and the results were compared with those of model tests.Resultsshow that the prefabricated steel frames have large lateral stiffness,good ductility,strong ability to resist horizontal load.And plastic deformations only occur on the truss beams and lean braces,which meets the seismic design principle of " strong column and weak beam".The lean braces play significant roles for resisting horizontal loads and deformation.The junction area between lean brace and truss beam is the weak area,and the top point on flange of channel's cross section of lean brace yields firstly,but the plastic strain does not further develop,and the stress on the web of the cross section is relatively small.