Provided in the present application is a modified separator of a metal negative electrode battery. The modified separator comprises a porous polyolefin separator and a thin film at least deposited on the surface of the porous polyolefin separator near a negative electrode material, the thin film comprising a diamond-like thin film. The diamond-like thin film has relatively high strength, enhances the strength of the separator, may impede the growth of metal dendrites, and changes the growth direction of the dendrites so that same grow horizontally, which thus prevents the metal dendrites from piercing the separator, effectively prevents the battery from short circuit failures due the the damage of the separator, and improves the usage safety of the battery, while simultaneously leading negative electrode metal to be evenly deposited and improving the stability of the metal negative electrode, thereby greatly enhancing the cycle stability of the battery.