The beam-to-column joint is the key connection of steel frame structure.Its connection property will directly influence the whole behavior of the frame structure under loading.The finite element method is applied to simulate the mechanical property of welded connection joint in beam-to-column structure.The mechanical behavior of welded connection joint under different stress conditions is analyzed.The characteristic of Mises stress along the length is revealed when different values of moment are applied.Displacement and Mises stress of welded connection joint with and without horizontal ribbed stiffener is analyzed comparatively.The results indicate that the displacement of welded connection joint with horizontal ribbed stiffener is obviously less than that of without stiffener.The displacement difference between with and without horizontal ribbed stiffener changes sharply when the moment reaches 65kN·m.The welded connection joint angle for the welded connection joint with horizontal ribbed stiffener increases exponentially with movement.Mises stress increases gradually from the edge of the cantilever beam to the joint of beamto-column ignoring the presence of horizontal ribbed stiffener.Mises stress is larger at beam-tocolumn connections and is the maximum in the joint zone of the column web plate.Mises stress in the cantilever beam and joint zone of the column web plate with horizontal ribbed stiffener is obviously less than that without horizontal ribbed stiffener.So bearing capacity of welded connection joint of beam-to-column will be improved by horizontal ribbed stiffener and the stress concentration of joints will be prevented.