As a new attractive material, special properties of Ultra-High Performance Concrete (UHPC) have opened new horizons to structural designers. The composite structure of UHPC and conventional concrete in this field is a new and practical idea which is presented for the optimization in design. This idea can be used for both new constructions and rehabilitation of old structures. The composite element of UHPC and reinforced normal concrete are more durability and resistivity in comparison to the conventional reinforced concrete elements at the same time, as the studies and practical uses are showing to us. It should be noted that the monolith performance of materials in every composite structure strongly depends on the bond performance between two different materials. There are few studies in the bond strength between UHPC overlays and conventional concrete substrate in the world, and Because of it in this study as one of the continues studies related to the UHPC in the University of Tehran, bond strength between this two materials with Four different substrate surface preparation method was investigated using pull off and slant shear tests. According to the tests results, the bond strength between the substrate and overlay highly depends on the substrate surface preparation methods and in the case of having a good surface preparation bond strength between UHPC and conventional concrete can simply pass the code's provisions.