The effects of grouting layer thickness, longitudinal reinforcement, reinforcement ratio and axial pressure on cracking development, failure pattern, direct shear strength, crack-slip curve and load-slip curve of concrete-concrete interface under direct shear loading were studied. The test results show that, for the interface without longitudinal reinforcement, the average failure loads of the specimens on the grouting layer with thickness of 1 and 10 mm were 1.69 and 1.14 times of that with the thickness of 20 mm, respectively. For the concrete-concrete interface with longitudinal steel bars, the average failure loads of the specimens with the reinforcement ratio of 0.9% and 1.8% were 1.58 and 1.89 times of that of the unreinforced specimens, respectively. In addition, the ductility of interfacial direct shear failure is significantly improved. However, for the reinforced specimens without stirrups, the failure pattern developed into concrete splitting failure by longitudinal steel bars, which can reduce the direct shear strength and ductility of the concrete-concrete interface. For the concrete-concrete interface under axial pressure, the average failure loads of the specimens under axial compressive stress of 11.6 and 23.2 MPa were 6.06 and 7.81 times of that of the unpressurized specimens, respectively. Under axial pressure of 23.2 MPa, the failure mode is transformed into the failure of cast-in-place concrete after the interface failure.