The utility model discloses an oil drainage device for oil span, the oil pan includes the bottom plate, be equipped with the mounting hole on the bottom plate, this jettison gear includes: the plug screw seat, it is inside to have a screw hole, and this screw hole link up the top surface and the bottom surface of this plug screw seat, the plug screw seat is installed the top of bottom plate, and have at least one oil drain hole on the outer peripheral face of this plug screw seat, this oil drain hole with the screw hole intercommunication, and plug screw, the plug screw includes basal portion and screw thread portion, the plug screw is followed the below of bottom plate is passed mounting hole and revolve to twist and to arrive on the plug screw seat. According to the utility model discloses an oil drainage device for oil span because the plug screw seat welds in the inside of oil pan bottom plate, can not occupy the too much space in engine bottom.