The variation rule of color of oxidation layer of TC18 titanium alloy and relationship between color of oxidation layer and corresponded mechanical properties were investigated via oxidative test within the temperature range of 100~1000 °C and mechanical property test. The results show that various colors of oxidation layer can be obtained. Mechanical properties of the alloy remarkably decrease and colors of the oxidation layer gradually turn dark with the increasing of oxidizing temperature. The relationship between color of oxidation layer and corresponded mechanical properties of TC18 titanium alloy was determined. When the oxidation color turns to be light green, the mechanical properties of the alloy significantly decrease which can not satisfy well the standard mechanical properties of TC18 titanium alloy.