Aiming at the problem that there is no standard test method for the shear strength of cement-based repair material and concrete interface, a double L direct shear test device was designed, which can effectively avoid the influence of bending stress and make pure shear failure at the interface. Based on this test device, the effects of concrete surface roughness, water content and interfacial agent type on the shear strength of mortar-concrete interface were studied. The results show that moderate roughness treatment is conducive to the improvement of shear strength, and the shear strength decreases when the roughness is too large. The higher the surface moisture content of concrete, the lower the interfacial shear strength will be, and the surface moisture content has a significant influence on the shear strength. The use of interfacial agent can strengthen the structure of interface transition zone, and the selection of appropriate interfacial agent according to the dry and wet conditions of concrete surface is helpful to improve the shear performance of the bonding interface.