Abstract: In order to improve the surface properties of magnesium alloy, TiAlCrN coating on AZ31 magnesium alloy was prepared by multi-arc ion plating.The effect of substrate bias voltage on the structure and properties of TiAlCrN coating was studied. The results show that when the bias voltage is 100 V, the amount of large particles on the surface of TiAlCrN coating is small, uniform and fine, and the surface quality of the coating is high.With the increase of bias voltage, the hardness and adhesion of TiAlCrN coating first increase and then decrease. When the bias voltage is 100 V, the microhardness and film-based adhesion of TiAlCrN coating reach the maximum of 2634.5 HV and 26.4 N respectively.With the increase of bias voltage, the oxidation weight gain of TiAlCrN coating samples decreases first and increases.When the bias voltage is 100 V, the oxidation weight gain rate is the lowest, and the oxidation resistance of TiAlCrN coating at high temperature is the best.When the bias voltage is 100 V, the TiAlCrN coating has a minimum corrosion current density of 4.286×10^-7 A·cm^-2, the corrosion resistance of the coating is the best.A dense and uniform coating can be obtained with appropriate bias voltage, and the corrosion resistance of the coating is improved.