The profiled steel structure of cold-formed square steel tubular has better seismic behavior and is suitable for reconstruction in seismic disastrous area. The joint is the key to the design of structure, so it needs further research on the mechanical properties. Using finite element software ANSYS to analysis two kinds of welding joints which under monotonic loading, the results show that: (1)The ultimate bearing capacity and yield load of improved joints greatly enhanced compared to conventional joints, and the plastic hinge moved to outward from the beam and column interface. (2)Until loading to the yield load, the improved joints has longer yield platform and better ductility. (3)The axial compression ratio has stronger effect on the conventional joints than improved joints on bearing capacity and initial stiffness.(4)Until loading to the ultimate load, degree of stress concentration on the improved joints is less than conventional joints, and the plastic hinge moved to outward, avoid brittle fracture of the joint.