A method for preparing a lithium alloy as an anode material includes the following steps: heating lithium metal into a molten state in an environment with a dew point not higher than −50° C. and an oxygen content not higher than 10 ppm; adding a transition metal to the molten lithium metal, maintaining the temperature for 5-15 minutes, and uniformly mixing to form a molten alloy; cooling the molten alloy to room temperature to obtain the lithium alloy as the anode material. The preparation method of the present invention is simple and feasible with less cost. The prepared lithium alloy as the anode material can effectively improve the coulombic efficiency and cycle lifespan of the lithium battery.