The invention relates to a high-weather-resistance acrylate resin composition and a preparation method thereof. The raw materials of the high-weather-resistance acrylate resin composition comprise the following components in part by weight: 10 to 30 parts of acrylate rubber powder 1, 10 to 30 parts of acrylate rubber powder 2, 30 to 60 parts of SAN resin 1, 5 to 20 parts of heat-resistant modifier, 5 to 15 parts of weather-resistant master batch, 0.3 to 3 parts of lubricant and 0.05 to 0.5 part of antioxidant. The preparation method comprises the following steps of: stirring the raw materialsexcept the weather-resistant master batch to obtain a mixture; adding the mixture from a main feed inlet of a double-screw extruder, and adding the weather-resistant master batch from a side feed inlet; and extruding and pelleting the raw materials by the double-screw extruder to obtain a sample. The high-weather-resistance acrylate resin composition prepared by the method has higher heat resistance, low-temperature impact resistance, weather resistance, excellent size stability and processing property, and is particularly suitable for automobile exterior trim parts, such as radiator grilles,rear-view mirrors, license plates, central pillar plates, outdoor triangular blocks and the like, with high requirements on weather resistance, heat resistance and low-temperature impact resistance.