Abstract: The tensile properties and the deformation mechanism of commercial pure titanium in the temperature range from -196 ℃ to 25 ℃ were investigated. The results show that with the decreasing of temperature, the yield strength and tensile strength increase gradually, the percentage elongation after fracture increases steadily to the highest at -140 ℃ and then decreases, and the percentage reduction of area increases gradually to 79% at-80 ℃ and then remains stable. Twins, high density dislocation and deformed structures are found in specimens stretched at 25 ℃, -80 ℃, -120 ℃ and -196 ℃. At 25 ℃, twins are seldom found, while at -80 ℃, -120 ℃ and -196 ℃, the densities of twins increase rapidly and the morphologies of twins are of great difference. Slipping is the dominant deformation mode in the course of tension at 25 ℃, while as the temperature decreases, twin plays an increasing role in the plastic deformation.