This invention discloses a method for separating high-temperature catalytically cracked oil gas rich in light hydrocarbons and catalyst dust. The method comprises: performing countercurrent direction contact between high-temperature reaction oil gas containing catalyst dust and the catalytically cracking raw material in a quench cooler to cool the high-temperature reaction oil gas and heat the catalytically cracking raw material, pumping out oil slurry containing catalyst dust, pumping out diesel oil fraction via a rectification column, and separating light hydrocarbons and gasoline fraction via a water-washing column. The method has such advantages as high heat-exchange efficiency, low cooling load at the overhead of the main rectification column, low pressure drop from the reaction oil gas to the inlet of the gas compressor, low energy consumption of the gas compressor, low coking at the bottoms of the quench cooler and the rectification column, and no emulsion phenomenon of the materials at the overhead of the main rectification column.