The invention discloses a cooling device in a biomass carbonizing furnace. The cooling device includes an integrated heat dissipate box, a heat dissipater, a storage bin, a cooling frame bottom trough, a cooling frame upper cover, a cooling frame, a control panel, and an internal cooler. The heat dissipater is installed on the integrated heat dissipate box. The storage bin and the control panel form a vertical structure and are respectively embedded in the integrated heat dissipate box. The cooling frame has a U-shaped structure and is connected to the integrated heat dissipate box to form anintegrated structure. In the cooling device, water is injected into a fixed water injection cylinder so as to drive the device through gravity of water, thus reasonably utilizing the water; the wateris pumped into a water pumping cylinder for spray cooling the furnace completely, so that the device has good cooling effect; finally, the water, after spraying, is pumped into a water circulating storage frame and then is injected into the fixed water injection cylinder again, thereby achieving circulation utilization of water and effectively saving water resources.