The invention relates to a device used for biomass gasification and active carbon combined production. The upper part of the device is provided with a material inlet, a material levelling device and a hydraulic lifting and descending mechanism. The middle part of the device is provided with a gasification reaction cavity. The gasification reaction cavity is provided with a secondary air injection pipe, a steam distribution pipe, a bridging-breaking driving lever, a carbon blocking device, a rotary fire gate and a fire-gate rotation rail. An external clamping cavity of the rotary fire gate is provided with a gasified gas extraction opening. The lower part of the device is provided with an active-carbon discharging cavity. The bottom of the device is provided with a sealing active carbon cooler. The device used for biomass gasification and active carbon combined production is advantageous in that: secondary air injection and an air-exhaust motor of combustible gas are adopted to control the thickness of a reaction layer and to provide the temperature needed for steam activation; steam and air mixing and forced gas distribution are adopted to achieve further activation of the gasified carbon, the produced combustible gas after purification can be used for electricity generation or burned in a boiler, and an active carbon product can be obtained at the same time. The device overcomes a problem of single product of traditional active carbon production devices, efficiently utilizes the biomass resources, increases the economic benefit, and is environmental friendly.