Abstract: This paper presents the direct shear tests of 129 Z shape new-old concrete bond specimens to study bond shear strength. Two types of specimen are considered: bonding before heating and heating before bonding. The influencing factors such as temperature (25℃-900℃), cooling way, interface roughness and interface adhesive agent on bond shear property are studied. Based on the tests, the paper presents the shear stress ~slipping curves of bonding interface and the corresponding unified calculation formula. In addition, a neural net predication model is established for the heating before bonding type specimens. The present systematic investigation of bond surface behavior of new-old concrete after exposure to high temperature may provide references for engineering application.