The invention relates to plastic alloy and a method for preparing the same, and belongs to the technical field of high-polymer materials. The plastic alloy comprises, by weight, 1-90 parts of polycarbonate, 1-90 parts of siloxane copolymerization polycarbonate, 1-90 parts of polyethylene terephthalate, 0.01-3 parts of nucleating agents, 0-10 parts of toughening agents and 0-10 parts of compatilizer. The plastic alloy and the method have the advantages that the rigidity and the heat resistance of the polycarbonate, the low-temperature impact resistance of the siloxane copolymerization polycarbonate and the solvent resistance, the excellent forming properties and the excellent abrasion resistance of the polyethylene terephthalate are integrated in the polycarbonate/siloxane copolymerizationpolycarbonate/polyethylene terephthalate plastic alloy; phase-state structures of resin can be adjusted by the nucleating agents, the superior performance of three components are kept at the high levels, accordingly, effects of complementing the superiority of the components can be realized, and the plastic alloy prepared by the aid of the method is excellent in low-temperature impact resistance,solvent resistance and abrasion resistance.