A transmission device capable of cooperating with a dual-power source and a driving method therefor, the transmission device includes a planetary gear assembly that is driven by the dual-power source; the planetary gear assembly comprises a sun gear, a rotating inner gear ring, and a planetary gear that is engaged between the sun gear and the rotating inner gear ring; the dual-power source comprises an input shaft, the input shaft being connected to the sun gear. The direction of the rotational movement of the planetary gear about the input shaft depends on the linear velocity V1 of pitch circle movement of the rotating inner gear ring and the linear velocity V2 of pitch circle movement of the sun gear.