Two direct shear experiments were designed， and the mechanical characteristics of steel keyed joints in the construction and service stage were analyzed with a combination of numerical analysis. It is shown that the joints depend on the contact compression between steel and concrete to transfer the shear force between the joints under the action of confining stress. The joints have high shear bearing capacity and good ductility. When the load-displacement curve enters the horizontal section， the joints can still bear large relative deformation， and its bearing capacity does not decrease. In the construction stage， the inelastic deformation of crossing-joint teeth should be used to control the temporary load design. In the service stage， the direct shear strength of the joints should be controlled by the shear strength of steel key’s material. The direct shear resistance of steel keyed joints can be calculated according to the shear formula. The material of the keys and the diameter of the crossing-joint teeth are the key factors affecting the bearing capacity of the joints.