The exploration of cathode materials with high energy density has been considered as one key for the development of magnesium batteries. The high magnesium storage capacity of CuS has been demonstrated at high temperature (over 100 °C), but its electrochemical performance at lower temperature still needed to be improved largely. Herein, we realize the high magnesium storage activity (over 300 mAh g−1) of CuS cathode at room temperature via adjusting electrode-electrolyte interface. In the full magnesium battery, CuS cathode achieves a high capacity of 119 mAh g−1 after 30 cycles at 50 mA g−1. Besides, the conversion-type storage mechanism has been certified via ex-situ XRD and so on. This work demonstrated CuS is a promising cathode material for magnesium battery.