After preheated in the condenser at the outlet of dimethyl ether fractionator, the crude methanol is sent to gasifier where the methanol is gasified by making ues of methanol reaction heat. Gasified methanol is warmed through heat exchanger at the reactor outlet up to about 220℃, and then is sent to the top of reactor via driving electric heater. It is catalyzed at the temperature of 260-280℃, and then is sent to methanol recovery column reboiler after cooled down in outlet heat exchanger. It will replace part of steam to heat DME distillation residue, after being cooled down to 100℃, it is sent to DME distillation column where DME is distilled. DMEis sent to product storage tank after cooled down.