Conveyor’s tension device is composed of bearing,screw rod,screw nut and track,etc. Rotating the screw rod can make bearing move along the track.screw nut is fixed on the bearing house. Screw rod can work under the compression type as well as work in the stretching type. But screw rod works better in stretching type. To use screw device, the stretch force is changeable. If rubber belt is elongation,the stretch force will become small. Thus we must check and adjust the stretch. Due to there exist error and difference by hands, the stretch force maybe big or small . So this tension device only can work in the short belt conveyor. The ribbon screw conveyor’s diameter is bigger than the tension roller.