The invention relates to a preparation method of a high-efficiency negative active material for a lithium ion secondary battery. Lithium-silicon alloys Li4.4Si, Li3.25Si and Li1.71Si are prepared by high-energy ball milling. The preparation method is simple, pollution-free and high in safety. At the same time, a suitable solvent is added in the high-energy ball milling to serve as a lubricant, thereby greatly improving the efficiency of an alloying reaction. A composite material is prepared from a lithium-silicon alloy together with pre-ball-milling silicon powder, graphite and carbon has a unique structure, which inhibits the volume expansion of materials during charging and discharging. Moreover, LixSi has high capacity and higher conductivity than pure silicon, and contains lithium, which can inhibit the formation of an SEI film in the first week and improve the first week coulombic efficiency of materials. Secondly, the experimental results of the invention show that the synthesized LixSi can be transformed into amorphous silicon after lithium removal, thereby effectively alleviating the volume change during charging and discharging, and exhibiting cycle performance far exceeding that of crystalline silicon. The high-efficiency negative active material is environmentally friendly, simple and feasible in preparation method and instrument and equipment, high in safety, and suitable for industrial production.