The invention discloses a modified polycarbonate material for preparing a shell of a water cup. The material is characterized by being prepared from the following raw materials in parts by weight: 500-520 parts of polycarbonate, 10-12 parts of long glass fibers, 10-14 parts of calcium silicate, 15-18 parts of poly-4-methyl-1-amylene, 4-6 parts of acrylic impact modifier ACR, 5-6 parts of tributyl citrate, 1-2 parts of anti-aging agent RD, 3-4 parts of calcium stearate, 2-3 parts of di(dioctyloxyl pyrophosphate) ethylene titanate and 10-12 parts of assistant. The modified polycarbonate material disclosed by the invention has better mechanical and physical properties, high strength, high elastic coefficient, higher impact resistance, good dimensional stability and good forming processability, is tasteless, odorless and harmless to a human body, and meets the sanitary safety.