NOVELTY - An engine gas is produced by conveying biomass and/or organic wastes to an airtight thermal cracking apparatus for thermal cracking or destructive distillation at 400-700 degrees C and negative pressure or normal pressure to obtain gaseous-phase substance, an ash component and solid carbon; transporting gaseous-phase substance to an airtight high-temperature thermal cracking apparatus having organic hydrocarbon substance, supplying heat to the apparatus or heating the gaseous-phase substance, and performing high-temperature thermal cracking under action of water vapor.    USE - Method of producing an engine gas.    DETAILED DESCRIPTION - An engine gas is produced by:    (A) conveying biomass and/or organic wastes to an airtight thermal cracking apparatus for thermal cracking or destructive distillation at 400-700 degrees C and negative pressure or normal pressure to obtain gaseous-phase substance, an ash component and solid carbon;    (B) transporting gaseous-phase substance to an airtight high-temperature thermal cracking apparatus having organic hydrocarbon substance, supplying heat to the apparatus or heating the gaseous-phase substance, performing high-temperature thermal cracking under action of water vapor on the gaseous-phase substance, and converting carbon deposit generated during the cracking process into flammable hydrogen and carbon monoxide to obtain a combustible gas comprising micromolecules;    (C) discharging the combustible gas generated by the thermal cracking from the high-temperature thermal cracking apparatus, and performing catalytic pyrolysis at 700-1100 degrees C on the discharged gaseous-phase substance in the presence of catalyst if the gaseous-phase substance has organic polymer like tar, heavy oil or aromatic hydrocarbon so that the organic hydrocarbon substances above C3 in the product gas exceeds the standard;    (D) discharging combustible gas generated after the catalytic pyrolysis, transporting discharged combustible gas to an airtight reaction container holding a high-temperature inorganic base in a melted fluid state at 700-1000 degrees C, absorbing and removing acidic gas using the high-temperature inorganic base in the melted fluid state, and simultaneously performing thermal cracking to the organic polymer substance into the low molecular combustible gas, and extracting the combustible gas treated by the high-temperature inorganic base in the melted fluid state from a refining device; and    (E) inputting the extracted combustible gas into a gas storage tank, adding gas stinking agent, extracting the gas sample, testing the heat value of the combustible gas which should be greater than or equal to 31.4 MJ/m3 under the standard conditions, adding high-heat value liquefied petroleum gas and/or hydrocarbon gases having less than 4C atoms if the heat value does not satisfy the standard so that the heat value of the gas reaches the standard.    DESCRIPTION OF DRAWING(S) - The drawing is a flow chart of a method of producing an engine gas. Drawing includes non-English language text.