The invention provides a large-taper medium-speed wire cut electrical discharge machining tool with a novel wire return arm. The tool comprises a supporting mechanism, a wire storing mechanism, a taper mechanism and a piece bearing mechanism. The wire storing mechanism, the taper mechanism and the piece bearing mechanism are arranged on the supporting mechanism. The wire storing mechanism is provided with a containing structure for placing cutting wires. The taper mechanism is located on one side of the wire storing mechanism. The wire storing mechanism conveys the cutting wires to the taper mechanism. The taper mechanism adjusts the angle of the cutting wires. The piece bearing mechanism is located below the taper mechanism. The piece bearing mechanism is provided with a locating structure for fixing a workpiece. The cutting wires on the taper mechanism cut the workpiece on the piece bearing mechanism. The taper mechanism sends the cutting wires back to the wire storing mechanism. A control cabinet adjusts the position and the direction of the taper mechanism and the piece bearing mechanism timely according to the technology requirement, the control efficiency is improved beneficially, the cutting precision is improved, thus, the working efficiency is improved, and the product quality is improved.