NOVELTY - Production of fuel oil comprises taking biomass as raw material and drying; adding raw material with heat carrier to rotary thermal cracking furnace to generate ash, oil, and gas; separating ash from oil and gas, condensing oil and gas to obtain bio-crude oil and noncondensable gas, introducing bio-crude oil into middle tank, gas-liquid separating noncondensable gas, and returning heat source to thermal cracking furnace; and distilling bio-crude oil, removing solid impurities, high boiling point fractionating, pouring in secondary steam catalytic tower, and carrying out catalysis reaction.    USE - Method for producing fuel oil (claimed).    ADVANTAGE - The method overcomes shortage of current technology and is reasonable. The fuel oil has high heat value, good liquidity, and good stability. The device is simple, convenient to operate, and energy-saving and has high production efficiency and strong raw material suitability.    DETAILED DESCRIPTION - Production of fuel oil comprises:    (A) taking biomass as raw material and drying, where biomass raw material is cotton straw pole and branch, sawdust, wood shavings, wheat straw, rice straw and rice hull, or 7 pts. wt. biomass and more than 2 pts. wt. waste plastic;    (B) adding raw material to built-in heat carrier rotary thermal cracking furnace for thermal coupling and thermal cracking reaction to generate ash, oil, and gas;    (C) separating ash from oil and gas, discharging ash, condensing oil and gas to obtain bio-crude oil and noncondensable gas, introducing bio-crude oil into middle tank, gas-liquid separating noncondensable gas to obtain bio-crude oil, and returning heat source of noncondensable gas to thermal cracking furnace; and    (D) distilling bio-crude oil at not greater than 360 degrees C, removing solid impurities, high boiling point fractionating, pouring in secondary steam catalytic tower, and carrying out catalysis reaction with catalyst.    An INDEPENDENT CLAIM is included for a built-in heat carrier rotary thermal cracking furnace comprising horizontal rotate furnace body, hearth, gas nozzle, gas leading-out tube, seal, static leading-out tube, feeding tube, sealed feeding mechanism, carrier roller, driving motor, and heat carrier copy plate.