TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: When the methanol fuel is methanol gasoline, the flash temperature during flash evaporation is 50-100 degrees C. When the methanol fuel is methanol diesel fuel, the flash temperature is 140-180 degrees C. When the methanol fuel is methanol lubricating oil, the flash temperature is 70-120 degrees C. During catalytic modification, the air flow is 200-2000/hour, reaction temperature is 200-500 degrees C and reaction pressure is 1-3 MPa. The catalytic reactor comprises a fixed bed reactor, a fluidized bed reactor, a slurry bed reactor, or a membrane reactor.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Materials: The catalyst for catalytic modification of the light components is iron or cobalt series catalyst obtained by Fischer-Tropsch synthesis, catalyst used for making methyl t-butyl ether (MTBE) by methanol, aromatic alkyl catalyst, or loaded solid acid or solid super-strong acid catalyst. The catalyst for catalytic modification of the heavy component is industrial catalyst, catalytically reformed catalyst or its modified product. Producing methanol fuel by mixing the modified oil product with the heavy component at the bottom of the flash tower comprises(A) injecting crude oil into a methanol fuel storage tank, adding methanol and uniformly mixing;(B) controlling methanol fuel by a material inlet valve and metering pump and gasifying the light component by a constant temperature heater, passing the light component through a reducing valve and introducing to the flash tower for separating from the heavy component;(C) introducing the separated heavy component into a condenser from the lower part through a liquid quantity meter and an adjusting valve to cool the heavy component;(D) pressurizing the separated light component by a compressor after passing through a buffer tank, then introducing the light component to the catalytic reactor through the quantity meter; and(E) condensing the modified light component by a condenser, and mixing with the heavy component through a valve and introducing the mixture into a methanol fuel product storage tank.