The invention relates to the technical field related to a straw extruder, in particular to a single-screw straw silking extruder, which aims to solve the technical problems of the bulky structure, lowprocessing efficiency and environmental pollution of the existing extruder. The following technical scheme is adopted: a central portion of an expansion tube is convexly provided with a connecting pipe penetrating a processing space, the axis of the connecting pipe is horizontally arranged and perpendicular to the axial direction of the expanding tube, and a plurality of overflow valves are arranged at the bottom of the outer body of the expanding tube, the overflow valve is connected with a draft tube; a feeding mechanism comprises a feeding main shaft horizontally arranged and driven to bemounted on a frame, a feeding screw fixed to the feeding main shaft, a feeding trough fixed to the frame, and a feeding hopper; the feeding screw is placed in the feeding trough, one end of the feeding trough is butt jointed with the connecting pipe, a plurality of water leakage holes are arranged at the bottom of the feeding trough, and the feeding hopper is fixedly connected directly above the feeding trough and is an upwardly expanding structure; the extruder also comprises a liquid-collecting tank for receiving and storing liquid flowing out of the leak holes or the draft tube.