The invention discloses a catalytic charing high efficiency halogen-free flame retardant PC (Polycarbonate)/ABS (Acrylonitrile Butadiene Styrene) mixture and a preparation method thereof. The mixtureis prepared from the following raw materials in percentage by mass: 37 to 67 percent of PC resin, 14 to 37 percent of ABS resin, 0 to 5 percent of compatibilizer, 0.1 to 0.5 percent of antioxidant, 5to 15 percent of chopped carbon fibers, 3 to 5 percent of organophosphate flame retardant, 0.5 to 3 percent of phenoxyposphazene and 0 to 1 percent of zirconium phosphate modified triazine silicon-based charring agent. The preparation method comprises the following steps: drying the raw materials except the chopped carbon fibers and fully mixing the raw materials in a high-speed mixer; then addingthe raw materials into a charging barrel of a co-rotating parallel twin-screw extruder through a main feeding bin; adding the chopped carbon fibers through a side feeding mode, carrying out melt extrusion and granulating. The mixture prepared by the preparation method disclosed by the invention has the advantages of high strength, good flame retardant performance, low addition amount of a flame retardant and the like; the mixture can be used in the fields of ultra-thin notebook casings, high-speed railway interior, unmanned aerial vehicle shells and other high-end electrical appliances.