Steel-bonded cemented carbide GT35 was fabricated from natural ilmenite by in-situ carbothermic reduction and vacuum pressureless sintering. The effects of Mo-doped on the mechanical properties and microstructures of GT35 composites were investigated. That the good mechanical properties of steel-bonded cemented carbide GT35 with 9wt% Mo were obtained at the same sintering condition that the density reached 6.223g/cm3 and the average bending strength reached about 1155.6MPa after heat treatment, but the hardness dropped the lowest value HRC 60.94 and the difference was not apparent with the change of Mo content. The additive of Mo is beneficial to be refinement of carbide particle size, sphericity of grains and formation of compact composite. In-situ reduction of natural ilmenite was a feasible way to fabricate good performance composite GT35 with a relative low cost.