Through the high temperature tensile creep experiments, the TC6 alloy creep strain-time curves were obtained, and the steady creep rate, the stress exponent and the apparent creep activation energy were calculated in the temperature range of 350~450 oC and different stresses. Microstructures of the alloy before and after creeping were analyzed by OM and TEM. On this basis the creep deformation mechanism was also studied. The results show that the steady creep rate increases with the increase of temperature or stress. The creep behavior of TC6 alloy in the range of 350~450 oC is controlled by double mechanisms of dislocation and diffusion. The boundary slip also has some effects on creeping.