The effects of different oxidation treatment temperatures on the oxidation layer color for TC21 titanium alloy were investigated, and the microstructure and mechanical property of the alloy after oxidation treatment were analyzed. The results show that after oxidation treatment, the color of oxidation layer presents particular change. The colors of oxidation layer become deeper with the increase temperature, and the mechanical property of TC21 titanium alloy is decreased. The oxidation color and the mechanical property of TC21 titanium have certain corresponding relations. When the oxidation treatment is 600 °C，the alloy shows dark blue, and the mechanical property could meet the requirements for utilization; when temperature of oxidation higher than 600 °C, the color of oxidation layer turns to darken, and the mechanical property could not meet the requirements for utilization