The invention provides a lathe machining clamping structure for thin-walled parts. The structure can clamp workpieces quickly, can be disassembled conveniently, and improves the processing efficiency greatly. The structure comprises a mandrel, wherein one end of the mandrel is clamped by a lathe jack catch, the mandrel is sleeved with a workpiece to be processed, and an end face of one side of the workpiece is axially positioned by a positioning ring surface of the mandrel. The structure is characterized in that an L-shaped clamping groove is axially formed in the surface of the mandrel, and a locking rod is mounted in the L-shaped clamping groove.