Abstract: The disclosure provides a reaction kettle, a polypeptide synthesis cleavage system and their use in polypeptide synthesis or cleavage. The reaction kettle comprises: (1) a kettle body; (2) a stirring device located at the upper part of the kettle body and extending to the interior of the kettle body; (3) a liquid feed port, a solid feed port, an inert gas inlet and an inert gas outlet located at the upper part of the kettle body; (4) a liquid discharge port and a liquid guiding groove at the bottom of the kettle body, wherein the liquid discharge port is located at the lowest point of the liquid guiding groove; (5) a filtering device located above the liquid guiding groove; (6) a solid discharge portpassing through the bottom of the kettle body and the filtering device; and (7) a discharge valve configured at the solid discharge port.