A new alloy belonging to Ti-AI-V-Si system has been developed on the base of Ti-6Al-4V, designated as TC4S. Experimental test results show that mechanical properties of TC4S have been improved evidently by proper adjusting the contents of Al and V, adding small amount of Si when compared with conventional Ti-6Al-4V alloy. The satisfied match among the strength, the ductility and the fracture toughness of the alloy has been reached, and meets the requirements of the design. The strength of TC4S alloy can be increased by 60 MPa-100 MPa on the condition of the slight damaging its plasticity and toughness, compared with Ti-6Al-4V ELI.