The invention discloses a quick replacement device for a furnace roller of a thermal treatment furnace. The quick replacement device comprises a clamping device, a mobile guide device and a fixed guide device. The clamping device comprises a trolley and a demounting platform fixedly provided with sliding blocks, and a gantry framework is fixed to the trolley. A bench clamp is fixed to the demounting platform. The quick replacement device further comprises a hydraulic jack fixed to the trolley; the hydraulic jack is connected with the demounting platform through a chain and a chain wheel. The mobile guide device comprises a first U-type bolt and a first cross beam in threaded connection with the first U-type bolt. The two ends of the first cross beam are in rolling connection with furnace rollers arranged on two sides of a furnace roller needing to be replaced in an adjacent mode correspondingly. The fixed guide device comprises a second U-type bolt and a second cross beam in threaded connection with the second U-type bolt. The arc section of the second U-type bolt is provided with at least one second idler wheel. The two ends of the second cross beam are fixedly provided with second supporting frames with magnets.