The invention discloses light-odor heat-resistance polystyrene resin and a preparation method thereof. The light-odor high-heat-resistance polystyrene resin comprises the following components in percentage by weight: 90 to 99.5 percent of high impact polystyrene (HIPS) resin, 0.1 to 5 percent of molecular sieve, 0.1 to 1 percent of antioxygen, and 0.1 to 4 percent of processing assistant, wherein the molecular sieve is a one-dimensional or multi-dimensional porous structure; and in the molecular sieve, the molar ratio of a silicon element to an aluminum element is 2 to 50. The preparation method of the flame-retarding polystyrene resin with high glow-wire ignition temperature comprises: weighing the components according a weight mixing ratio; mixing the components in a high-speed mixer for 3 to 5 minutes; and extruding and granulating the mixed material in a screw extruder. The light-odor high-heat-resistance polystyrene resin has high heat resistance and light odor and meets the requirements of an environment-protection trend.