The invention discloses a photodiffusion PC material with high flame-retardant performance and a preparation method thereof. The PC material is prepared from PC granules, PC powder, a photodiffusion agent, a brominated flame retardant, an organic-silicon flame retardant, a main antioxidant, an auxiliary antioxidant, an ultraviolet light absorber and a lubricant. The preparation method comprises the steps as follows: 1) drying the PC granules and the PC powder; 2) preparing photodiffusion agent master batch; 3) fully and uniformly mixing the PC granules, the photodiffusion agent master batch, the brominated flame retardant, the organic-silicon flame retardant, the main antioxidant, the auxiliary antioxidant, the ultraviolet light absorber and the lubricant; 4) adding the material in step 3) to a twin-screw extruder for extrusion granulation to obtain the photodiffusion PC material with high flame-retardant performance. The photodiffusion PC material with high flame-retardant performance has the advantages of high light transparency, high haze, high flame-retardant performance and the like, has excellent comprehensive performance and can be widely applied to electrical lighting and other fields. The preparation method is simple, the process operation is easy to realize, the production cost is low, and industrial production is facilitated.