The invention discloses a battery box cover used for new energy automobiles. The battery box cover used for new energy automobiles is prepared from, by mass, 55 to 65 parts of phenolic resin, 35 to 45parts of epoxy resin, and 50 to 70 parts of glass fiber cloth. The preparation method comprises following steps: 1, phenolic resin, epoxy resin, and glass fiber cloth are mixed at the weight ratio, and are subjected to dipping and drying to prepare a pre-paved layer, wherein the pre-paved layer is a prepreg; 2, mould pre-heating is carried out, wherein a pre-prepared battery box mould is cleaned,and is subjected to mould pre-heating; 3, compression molding is carried out, wherein the prepreg is introduced into the pre-heated mould for compression molding, and after molding, demoulding is carried out; and 4, examination and packaging are carried out, wherein products obtained through demoulding are subjected to trimming, examination, and packaging. According to the preparation method of the battery box cover used for new energy automobiles, the epoxy modified phenolic prepreg is adopted in compression molding of the automobile battery box cover, so that flame resistance, corrosion resistance, and weight reduction are realized with ensured strength.