NOVELTY - Synthesizing methanol by carbon monoxide (CO), carbon dioxide (CO2), and hydrogen (H2) comprises: (a) purifying and compressing synthesis gas to obtain fresh gas; (b) exchanging heat between the gas for entering to tower and the gas for exiting from tower; and (c) conveying the gas phase obtained from separation of crude methanol and water to a water scrubbing tower.    USE - The method is useful for synthesizing methanol by CO, CO2, and H2 (claimed).    ADVANTAGE - The invention is reliable, the process is short, the operation is convenient and stable, and the investment for equipment is less; in actual production, the yield of methanol can be improved 10-15%.    DETAILED DESCRIPTION - Synthesizing methanol by CO, CO2, and H2 comprises: (a) purifying and compressing synthesis gas to obtain fresh gas, mixing the fresh gas with unreacted circulation gas to obtain gas for entering to tower, exchanging heat between the gas for entering to tower and the gas for exiting from tower, heating up to 190-230 degrees C, and then entering to synthesizing tower, carrying reaction on CO, CO2, and H2 in the synthesizing tower to generate methanol, heating up to 220-280 degrees C; (b) exchanging heat between the gas for entering to tower and the gas for exiting from tower, cooling down to 80-100 degrees C, entering to a water cooler, condensing the unreacted reaction gas and the generated methanol by water in the water cooler to 30-50 degrees C, carrying gas-liquid separation in a separator for crude methanol, to obtain condensed crude methanol and water namely the separated liquid phase, and obtain unreacted synthesis gas namely the gas phase, where the unreacted synthesis gas contains saturated methanol steam under the working condition; and (c) conveying the gas phase obtained from separation of crude methanol and water to a water scrubbing tower, scrubbing the unreacted gas by the water with spraying density of 0.2-8 m3/m2/hour, to obtain the unreacted gas in which the volume percent content of the saturated methanol steam is reduced to 0.1% below, taking most of the unreacted gas as circulation gas to use, taking a small part as vent gas to convey to a hydrogen production device to recover H2, conveying the recovered H2 back to system to act as methanol raw material, conveying the analysis gas obtained from recovering H2 to a fuel system to act as fuel, where the circulation gas is about 4-10 times of the fresh gas, and the vent gas is about 4-15% of the quantity of the fresh gas, and then mixing the scrubbing liquid from the water scrubbing tower kettle with the methanol separated from the separator for crude methanol, to obtain mixed liquid with mass content of 80-92%, and then entering to a rectifying system to obtain the methanol.