The invention relates to the field of bulk cargo conveying of belt conveyor, in particular to a conveying material-smoothening control device and method of a belt conveyor. A dual-system material-smoothening automatic-balancing regulating control device comprises a moving trolley, a trolley track, a track fixing frame, a trolley traveling motor, a moving chute, a dual-system left chute, a dual-system right chute and an electronic scale. A dual-system material-smoothening automatic-balancing regulating control method comprises the steps that a unit displacement distance, a test time interval and a deviation threshold value of the moving chute are set, the electronic scale measures the flow of material on a dual-system downstream belt conveyer every other test time interval, and if deviation of the left material flow and the right material flow of the dual-system downstream belt conveyer is greater than the deviation threshold value, the moving chute moves towards the side with the lower material flow. The dual-system material-smoothening automatic-balancing regulating control device and method ensure that the locating point of the moving chute is in a dual-system material-smoothening balancing state all the time, avoid material leakage and accumulation accidents caused by flow deviation of the moving chute, guarantee that a conveying belt operates normally, and facilitate safety production and productivity improvement.