The present invention discloses a gas-charcoal cogeneration biomass gasification combustion system, which is used in the technical field of biomass gasification equipment, and comprises a gasification furnace, a boiler and a soft water box, wherein the top portion of the gasification furnace is provided with a material inlet and a biomass fuel gas outlet, the bottom portion of the gasification furnace is provided with a material discharging port, a rotation grate is arranged on the bottom portion of the gasification furnace and above the material discharging port, and comprises a plurality of rotation roller cylinders arranged side by side, material discharging gaps are arranged between the adjacent rotation roller cylinders, a cooling water chamber connected to the soft water box through a first circulation water pipe is arranged in the rotation roller cylinder, the boiler comprises a boiler cavity, a combustor and a boiler water box, the boiler water box is provided with a steam outlet and a soft water inlet connected to the soft water box, and the biomass fuel gas outlet is connected to the combustor. With the technical scheme of the present invention, the requirements of the market can be met, the environmental protection pressure can be alleviated, and the benefits can be provided for the society.