The invention provides a transparent flame-retarding polycarbonate composite material and a preparation method thereof. Polycyanamide, a multi-amino compound, modified transparent filler and the likeare added into components; in a preparation process, all the components are prepared into a No. 1 material, a No. 2 material and a No. 3 material respectively; then the components react with the modified transparent filler on the basis of the No. 1 material and the No. 3 material; meanwhile, technological parameters including a proportioning amount and mixing temperature, a stirring speed, stirring time, extruding temperature and the like of the components are strictly controlled so that the reaction mixing effect of the components is increased, the synergetic effect is realized and the performance of products is greatly improved; a test proves that the polycarbonate composite material prepared by the preparation method has excellent flame-retarding performance; in a flame-retarding test,flame is extinguished after the shortest time of 4s and the flame-retarding performance reaches a V-0 grade; the polycarbonate composite material also has good light transmittance and can reach 84 percent at maximum; the polycarbonate composite material can be widely applied to the fields of lamps and the product has good light transmittance, flame-retarding performance and a long service life.