Because of low density, high specific strength, corrosion resistance to sea water and so on, titanium and its alloys are the ideal metal materials for shipbuilding. Four different alloys, i.e. Ti75, TiB19, Ti31 and Ti91,having good comprehensive properties with different strength scale, were designed and developed by Northwest Institute for Nonferrous Metal Research. Based on these four alloys, the national Ti alloy's system of China has been set up.