The old-new concrete interface is the weakest part in the composite structure, and there are a large number of microcracks on the interface. In order to study the mode II fracture performance of the bonding surface of old-new concrete, the effect of planting rebar and basalt fiber is investigated. Nine Z-shaped old-new concrete composite specimens with initial cracks are made. Nine shear fracture load-displacement curves are obtained, and the failure process and interface fracture are discussed. On this basis, the mode II fracture toughness and fracture energy are obtained. The regression equations for fracture toughness and fracture energy are deduced with analysis of variance (ANOVA). The results show that fracture toughness and fracture energy increase with the increase of planting rebar number and basalt fiber content. With the increase of the planting rebar number, mode II fracture toughness and fracture energy increase more significantly. Planting rebar is the major factor for mode II fracture performance.