The invention discloses a polycarbonate resin compound and a preparation method thereof. The polycarbonate resin compound comprises the following components: 80 to 99.5 portions by weight of polycarbonate resin or polycarbonate resin alloy, and 0.5 to 20 portions by weight of organic silicon rubber. The preparation method comprises the following steps: (1) premixing, namely, adding the polycarbonate resin or the polycarbonate resin alloy and the organic silicon rubber into a mixer, and premixing the materials for 1 to 6 minutes with the rotating speed of 100 to 800 revolutions per minute at the mixing temperature of between 20 and 50 DEG C; and (2) squeezing granulation, namely adding the premixed materials into a double-screw extruder to carry out squeezing granulation, wherein the temperature of each section of the double-screw extruder is between 180 and 300 DEG C during extrusion, the rotating speed of screws is 100 to 500 revolutions per minute, and the rotating speed of a feeder is 10 to 60 revolutions per minute. The polycarbonate resin compound prepared by the method has good liquidity, thermal stability and impact resistance, and belongs to the field of polymer material modification.