The invention provides a PC alloy material and a preparation method thereof. The PC alloy material is prepared by mixing the following components in parts by weight: 100 parts of PC resin, 18-25 parts of aluminium coated modified magnesium oxide powder, 12-16 parts of surface modified aluminum oxide powder, 5-8 parts of rutile type titanium dioxide, 6-12 parts of modified graphene, 3-8 parts of a composite toughing agent, 3-6 parts of a composite flame-retardant agent, 8-20 parts of a compatilizer, 1.5-2.5 parts of a silane coupling agent, 0.5-1.5 parts of an oxidation inhibitor, 0.5-1.2 parts of an anti-dripping agent and 1.5-2 parts of an ultraviolet absorber. According to the PC alloy material, the PC resin and the various kinds of powder are fused; the powder is modified so that the powder can be fused in the PC resin fused body well; and the composite flame-retardant agent and the composite toughing agent are innovated, so that the prepared PC alloy material has good mechanical property, thermal property, optical property and electrical property, belongs to a brand-new PC alloy material, and has wide market popularization and application prospects.