Disclosed is a method for making dimethyl ether by reactive distillation. The method provides a reactive distillation tower with a top, a bottom, and rectification, reaction and stripping zones defined therein. The top of the reactive distillation tower is retained at 25° C. to 40° C. while the bottom of the reactive distillation tower is retained at 84.6° C. to 170° C. Each of the rectification, reaction and stripping zones includes several sieving trays. The reaction zone of the reactive distillation tower is filled with catalyst. The pressure in the reactive distillation tower is lower than 8.0 bars. Methanol is introduced into the reactive distillation tower so that the methanol travels from the reaction zone toward the bottom for contact with the catalyst to provide a top stream and a bottom stream. The top stream includes dimethyl ether. The bottom stream includes water and a remaining portion of the methanol. Finally, the dimethyl ether is collected in the top of the reactive distillation tower. The purity of the collected dimethyl ether is higher than 99%.