In order to study the influence of the yield strength f_y of the shear reinforcement and the concrete cover thickness h on the direct shear performance of the monolithically cast concrete interface, a push-out test of 12 Z-shaped specimens was carried out. Based on the experimental phenomenon and the measured load-slip curve of the interface, the interface shear force transfer mechanism was revealed. According to the test value of the bearing capacity of the specimens, the calculation formulas of the interface direct shear bearing capacity of the standard ACI, PCI and AASHTO were evaluated and analyzed. The results show that when f_y increases from 400 MPa to 600 MPa or h increases from 20 mm to 40 mm, the direct shear strength and stiffness of the interface do not change significantly, while the change of h will cause the different interface failure modes; The cohesive force of concrete has a great contribution to the direct shear bearing capacity of the interface; The three standard calculation formulas can be applied to engineering design, while the ACI and PCI calculation formulas are too conservative, and the AASHTO calculation formula is of great accuracy.