The invention discloses a separation process for preparing low-carbon alkene gases through conversion of methanol and aims to solve the problems that high-purity products such as hydrogen, methane, ethane and propane cannot be obtained and oxygen and carbon monoxide in dimethyl ether and gas impurities cannot be effectively eliminated in the prior art. According to the alkene gas streams through conversion of methanol, eliminating steps of oxygen and carbon monoxide are added, the alkene gas streams through conversion of methanol after elimination of oxygen and carbon monoxide sequentially passes six knockout drums and then enters a low-pressure demethanizer, a deethenizer, an acetylene hydrogenation reactor, an ethylene rectification tower, an allylene hydrogenation reactor and a propylene rectification tower for separation, the liquid from the bottoms of the first four knockout drums sequentially enter the middle-upper portion of the demethanizer, and the liquid from the bottom of the fifth knockout drum enters the upper portion of the demethanizer or returns to a section of a compressor. The separation process for preparing the low-carbon alkene gases through conversion of methanol can obtain products such as polymer grade ethylene, propylene, and the high-purity products such as hydrogen, methane, ethane and propane.