The invention discloses a polystyrene brittle modified plastic. The polystyrene brittle modified plastic is prepared from polystyrene resin, rubber and additives, wherein the additives are a filler, a stabilizer, a coupling agent and an antioxidant, the rubber is butadiene styrene rubber and butadiene rubber, the filler is silica, the stabilizer is barium stearate, the coupling agent is vinyl triethoxy silane, and the antioxidant is a phosphite antioxidant. By virtue of the mode, the invention provides the polystyrene brittle modified plastic which is good in the size stability and the rigidity, is easy in processing and coloring, is high in the product glossiness and the like; and meanwhile, with the adoption of the polystyrene brittle modified plastic, as the tenacity of the polystyrene is improved, the polystyrene brittle modified plastic is suitable for manufacturing various electric appliance parts, equipment housings, instrument parts, refrigerator linings, vessels, food packages, disposable utensils and the like.