The utility model relates to a furnace body structure of a biomass gasification furnace. An inner barrel is arranged in the upper half part of an outer barrel, the edge at the upper end of the inner barrel and the edge at the upper end of the outer barrel are welded and sealed through an annular flange; the edge at the lower end of the inner barrel and the inner wall of the outer barrel are welded and sealed through a first annular plate; a water jacket is formed between the outer wall of the inner barrel and the inner wall of the outer barrel; the wall of the outer barrel is provided with a water inlet and a water return port; the inner wall surface of the lower half part of the outer barrel is provided with a fire-proof insulated wall; a second annular plate is welded and fixed on the edge at the lower end of the outer barrel; an ash blocking ring and a water seal ring are coaxially arranged and are welded at the bottom of a third annular plate, the ash blocking ring is positioned inside, and the water seal ring is positioned outside; multiple ash scraping plates are welded on the inner wall of the ash blocking ring and are uniformly distributed along the circumferential direction of the ash blocking ring; the middle of a furnace body is provided with a feed port; and the upper part of the furnace body is provided with a gas outlet. The furnace body structure is ingenuous and reasonable in structure, and can be used for producing steam, the gas outlet temperature is lowered, the temperature stability of a combustion layer is ensured, thereby ensuring uniform combustion and sufficient gasification, and improving the heat value and the gas production rate.