The present invention relates to a method for preparing ethylene by using ethanol. A purpose of the present invention is to solve the problems of unreasonable production process for preparing the ethylene by ethanol dehydration, and large energy consumption of the device in the prior art. The method of the present invention adopts the following technical scheme that: the reaction product generated from the ethanol dehydration is subjected to heat exchange with a raw material ethanol, and then enters into a water washing system and an alkaline washing system to remove ethanol, acetaldehyde, carbon dioxide and other impurities; the resulting crude ethylene after the water washing and the alkaline washing is subjected to compressing and drying, and then enters an ethylene distillation tower, wherein the crude ethylene containing hydrogen, methane and carbon monoxide is obtained from the top of the ethylene distillation tower, heavy components containing ethane, ether, and C3<+> are discharged from the bottom of the ethylene distillation tower; the partial crude ethylene from the ethylene distillation tower reflows to the ethylene distillation tower, and the partial crude ethylene from the ethylene distillation tower enters a dehydrogenation tower, wherein hydrogen, methane, carbon monoxide and other light components are separated from the top of the dehydrogenation tower, the ethylene product is obtained from the bottom of the dehydrogenation tower, wherein the boiling points of the light components are lower than the boiling point of the ethylene. With the technical scheme of the present invention, the problems in the prior art are solved well. The method can be used for industrial production of the ethylene by the ethanol dehydration.