Based on bi material wedge splitting test(WST), the fracture property of interface between engineering cementitious composites and concrete was investigated. The effect of three different levels of roughness on ECC concrete interface fracture properties and failure mode was also discussed. By adopting interface mechanics, both kinked crack failure and interface failure and the influence on kinked crack failure by different interface roughness were analyzed. It is discovered from the study that interface failure occurs in the specimens with smooth interface while interface failure with small angle deflection occurs in the specimens with rough interface. When the interfacial roughness is improved, bonding interface strength can be enhanced to a certain extent, and the interface crack during the loading process kinks into ECC more easily due to interface crack trapping mechanism can be guaranteed to achieve. In practical engineering applications, interfacial roughness should be enhanced to avoid interface failure and ECC should be used if the type of loading is unknown.