The oxidation characteristics and the effect of oxidation on mechanical properties of Ti600 alloy at 600 oC were researched. The results show that the increase of oxide skin is nearly controlled by the diffusion of O element. After 600 oC thermal exposure for a long time, the surface is mainly composed of TiO2 and Al2O3. The solution O element mainly exists inside octahedral interstice, which leads to almost changeless “a” and “b” and obviously increased “c” of hcp a-Ti crystal lattice. Through the comparison of mechanical properties between the samples with oxide skin and without oxide skin, it can be concluded that the decrease of plasticity is mainly due to the oxidation of the alloy. Thus it is very necessary to adopt surface protection for Ti600 alloy for 600 oC application.