In this study, the microstructure and interface of steel-bonded TiB2 were adjusted by adding Mo2C, so as to improve its comprehensive mechanical properties. The addition of Mo2C led to the formation of two kinds of core-rim structures, including TiB2 core-(Ti, Fe, Ni, Cr, Mo)B rim, and TiC core-(Ti, Fe, Ni, Cr, Mo)C rim. Micro - nano scale of TiB2, TiC and (Mo, Cr)C particles were formed in the steel-bonded TiB2. The introduction of Mo element caused the redistribution of elements in Fe-based binder phase, and two types of binder phases were generated, one was Ni-rich binder phase, and the other was Cr-rich binder phase. A full coherent interface was formed between the core and rim phase, and the amorphous metal thin layer was formed between the rim and binder phase. A coherent interface was formed between TiB2 and (Mo, Cr)C phase, (Mo, Cr)C and Ni-rich binder phase, as well as TiB2 and Ni-rich binder phase. Both the coherent interface and amorphous metal thin layer greatly enhanced the interface bonding strength, and improved the strength and toughness of the steel-bonded TiB2. The steel-bonded TiB2 with 6.0 wt% Mo2C exhibited excellent comprehensive mechanical properties, and its relative density, hardness, transverse rupture strength and fracture toughness were 99.94 ± 0.06%, 92.3 ± 0.5 HRA, 1278 ± 37 MPa and 10.90 ± 0.28 MPa·m1/2, respectively.