The invention provides a method for reducing energy consumption of a device for preparing olefins from an oxy-compound. The method is characterized in that sewage containing methanol or dimethyl ether enters a sewage stripping tower, the stripping gas at the top of the sewage stripping tower after stripping enters a reflux tank at the top of the sewage stripping tower after undergoing heat exchange in an oxy-compound raw material-stripping gas heat exchanger, the concentrated water containing methanol or dimethyl ether flowing out of the bottom of the reflux tank entirely returns to the upper part of the sewage stripping tower as tower top reflux, or a part of the concentrated water returns to the upper part of the sewage stripping tower as tower top cold reflux and the other part of the concentrated water is mixed with the oxy-compound raw material feed and is sent to a reactor for reprocessing; and the non-condensable gas at the top of the reflux tank is sent to the reactor for reprocessing. The method has the advantages that the high-temperature level heat energy of the stripping gas at the top of the sewage stripping tower can be farthest recovered, the vapor dosage can be reduced, the dosage of the circulating cooling water can be reduced and the total energy consumption of the device can be reduced.