The invention relates to a polycarbonate composition for 3D printing technology and a preparation method thereof. The composition is composed of the following components according to a certain ratio: polycarbonate resin, SAN-GMA, nano silicon dioxide, a flexibilizer, an antioxidant, and a lubricant. The diameter of the screw rod of an extruder used in alloy preparation is 58 mm, and the length / diameter ratio is 60. The preparation method comprises the following steps: adding PC resin, SAN-GMA resin, nano silicon dioxide, a flexibilizer, an antioxidant, and a lubricant into a mixing and stirring machine, mixing, transferring the mixture to a double-screw-rod extruder, blending, melting, extruding, and granulating to obtain the polycarbonate composition for 3D printing. Compared with the prior art, during the preparation process, the PC / ABS melting range is shortened, furthermore, nano silicon dioxide is added to enhance the heat transferring performance of the polycarbonate composition, and the warping problem during the 3D printing process is solved.