The present invention provides a large-tonnage slender externally powered rail-mounted unloading skip, comprising an upper bin body and a lower bin body that are respectively formed by an inner lining plate and an outer plate fixed together via a number of pin shafts, a self-locking gate, and a gate opening device. A loading opening and a coal baffle plate that is used to block coal when the coal is loaded are arranged on the upper part of the upper bin body, a self-locking gate composed of a sector gate plate and unloading rollers is arranged on the lower bin body, a coal chute is arranged on the lower part of the self-locking gate, the upper bin body and the lower bin body are connected together through flanged connection, and channel irons are welded around the walls of the upper bin body and lower bin body respectively; when the skip is at an unloading position, externally powered telescopic push rods push the unloading rollers to move in an unloading rail of the slide block, so that the self-locking gate is opened, and the coal is unloaded along a coal chute. With the reliable connection between the upper bin body and the lower bin body, effective and convenient fixing of the lining plate, and reliable opening of the gate, the skip can meet the production requirements of 10-million tonnage large-size shafts.