Abstract: Alkaline solution treatment was used to purify B₄C powder and enhance the wetting ability between the B₄C powder and the Mg-Li matrix. The results show that both of the specific surface and B₂O₃ decrease. Tensile strength and density of the pre-mixed alloy prepared by the B₄C powder after alkaline treatment increase. Fewer agglomerates and uniform formation are proved in the metallographic structure of the B₄C/Mg-Li composite (Mg-15Li-2Al-6B₄C). The tensile strength of B₄C/Mg-Li composite increases 21.53% compared with that prepared by B₄C without alkaline solution treatment. Results indicate that the alkaline solution treatment of B₄C powder can improve the strengthening effect of the boride in-situ reacted in the B₄C/Mg-Li composite.