The work aims to enhance the surface hardness and wear resistance of magnesium alloy. Provide the optimal preparation temperature of excellent properties of the film. A hydrogen-containing DLC film was prepared on the surface of AZ31 magnesium alloy by plasma-enhanced chemical vapor deposition (PECVD) technology. The effects of deposition temperatures on the thickness, surface morphologies, hardness, Young’s modulus, wear resistance, bonding force and the contents of sp3 bond were studied. The corresponding mechanism of the influence of temperature was also discussed. The results show that the deposition temperatures have significant effect on the microstructures and properties of the DLC film on the surface of AZ31 magnesium alloy. At lower temperatures, the energy of carbon particles were lower. Therefore, the carbon particles cannot be injected into the subsurface of the film. They can only stay on the surface and growth by the form of sp2 hybrid. With the increase of temperature, the energy of carbon particles were increased and more sp3 hybrid bonds were formed. The hybrid forms of DLC film are mainly sp3 bonds at the deposition temperature is 75 ℃. At this temperature, the value of film thickness is about 7.67 μm, the value of film hardness is 5.95 GPa, the value of film Young‘s modulus is 43.2 GPa and the value of film friction coefficient is only 0.03. As the further increase of temperature, the energy of the carbon particles are increased continually. Therefore, the carbon-hydrogen bonds are broken under the bombardment of high energy carbon particles. The bombardment can result in the desorption of hydrogen, which can reduce the content of sp3 hybrid bond in the film. Therefore, the mechanical properties such as hardness and wear resistance are decreased. In this study, the optimum temperature for the preparation of DLC film on the surface of AZ31 magnesium alloy is 75 ℃.