NOVELTY - A multiple-effect rectifying technology of methanol comprises: (a) pumping crude methanol containing impurities of hydrogen, carbon monoxide, carbon dioxide, nitrogen, methane, dimethyl ether, methyl formate, acetone, ethanol, water, polylol, and alkane in crude methanol feeding pre-heater; (b) rectifying; (c) treating methanol; (d) letting the methanol solution of the first pressurizing tower flow in second pressurizing tower; (e) letting the methanol solution of the second pressurizing tower flow in normal pressure tower; and (f) boosting the methanol solution at the normal pressure tower.    USE - The process is useful for multiple-effect rectifying the methanol (claimed).    ADVANTAGE - The process provides an energy-saving methanol multiple-effect rectifying technology process with lower energy consumption, more steady production process, easier controlling product quality, and higher methanol recovering rate and equivalent investment compared with the three-effect rectifying technology.    DETAILED DESCRIPTION - A multiple-effect rectifying technology of methanol comprises: (a) pumping the crude methanol containing impurities of hydrogen, carbon monoxide, carbon dioxide, nitrogen, methane, dimethyl ether, methyl formate, acetone, ethanol, water, polylol, and alkane in crude methanol feeding pre-heater (26a,26b) through the crude methanol feeding pump (25); pre-heating at 65-80 degrees C; letting it enter the pre-rectifying tower (1); (b) rectifying crude methanol through the pre-rectifying tower, cooling at 65 degrees C and 38-45 degrees C through the light component steam left from the tower top serially passing through the first grade condenser (2) and the second grade condenser (3) at tower top of the pre-tower by the steam, sending the condensable liquid back to the pre-tower top reflow tank (4) to reflow via pipeline; where the incondensable gas enters the washing tower (30); the washed incondensable gas via the washing tower is sent to the heating furnace to be used as fuel or go to the torque; and the washing liquid is sent to the pre-rectifying tower top reflow tank; (c) treating the methanol through the pre-rectifying tower, boosting through the prognosis crude methanol pump (6) via the bottom of the pre-rectifying tower, exchanging heat by the prognosis crude methanol heat exchanger (7a,7b) at 130-140 degrees C, letting it enter the lower part of the first pressuring tower; condensing the methanol steam at lower top of the first pressuring tower via the re-boiler (15) of the bottom of the second pressuring bottom; where one part is used as tower top reflow of the pressuring tower (8); the remaining part is exchanged heat by the crude methanol feeding pre-heater and the refine methanol cooler (27) to be send in refine methanol product tank; and the bottom of the first pressuring tower adopts 0.5 or 1.0 MPaG saturated vapor as heat source; (d) letting the methanol solution of the bottom of the first pressurizing tower flow in the lower part of the second pressurizing tower (12); condensing the methanol steam at top of the second pressuring tower by the re-boiler (20) of the bottom of the normal pressure tower; where one part is used as tower top reflow of the second pressuring tower; the remaining part is exchanged heat by the crude methanol feeding pre-heater and the methanol cooler to enter the refine methanol product tank; (e) letting the methanol solution of the bottom of the second pressurizing tower flow in the lower part of the normal pressure tower (16); condensing the methanol steam at top of the normal pressure tower by the tower top air cooler (17) of the normal pressure tower; where one part is send to the tower top of the normal pressure tower to reflow; and the remaining part is exchanged heat by the refine methanol feeding pre-heater and the methanol cooler to enter the refine methanol product tank; and (f) boosting the methanol solution at the bottom of the normal pressure tower through a pump, sending to lower part of the recovery tower (21); condensing the methanol steam of the tower top of the recovery tower by the bottom re-boiler (5) of the rectifying tower; where one part is used as tower top reflow of the recovery tower; and the remaining part is entered in the refine methanol product tank; producing the fusel oil in the recovery tower from lower side line of the recovery tower; where the wastewater discharged from the tower bottom of the recovery tower is exchanged heat; one part is used as leaching water of the rectifying tower to be send in the incondensable gas washing tower; the other part is send to the sewage treating device by wastewater pump or directly discharged; and the recovery tower bottom adopts 0.5 MPaG saturated vapor as heat source.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic diagram of the device used in multiple-effect rectifying technology of methanol.    Pre-rectifying tower (1)    First grade condenser (2)    Second grade condenser (3)    Reflow tank (4)    Re-boiler (5,15,20)    Prognosis crude methanol pump (6)    Prognosis crude methanol heat exchanger (7a,7b)    Pressuring tower (8)    Second pressurizing tower (12)    Normal pressure tower (16)    Air cooler (17)    Recovery tower (21)    Crude methanol feeding pump (25)    Crude methanol feeding pre-heater (26a,26b)    Refine methanol cooler (27)    Washing tower (30)