The invention belongs to the technical field of transmissions and particularly relates to a transmission based on variable-diameter belt wheels. The transmission comprises fixed wheels, a belt and the variable-diameter wheels. The variable-diameter wheels drive the fixed wheels to rotate through the belt. The diameter of the fixed wheels is unchanged in the transmission process, the diameter of the variable-diameter wheels changes according to torque transmitted by an input shaft, the diameter changes, the transmission ratio of the two belt wheels changes, and the speed change purpose is achieved. The belt is further provided with a belt pre-tensioning mechanism during transmission, after the diameter of the variable-diameter wheels changes, the required effective belt length during transmission changes, the change is counteracted through the belt pre-tensioning mechanism, and it is guaranteed that the belt is always in the tensioned state during speed change; if the variable-diameter wheels and the wheels with the fixed diameter are together used as the automobile accelerator, when the transmission climbs the slope or speeds up for overtaking, an automobile can obtain the large torque and the acceleration automatically; and the transmission has the high use effect.