The invention discloses a tool for manufacturing a gasket. A first component, a second component, a third component and a fourth component are included. The first component is provided with a first groove formed in the upper end of the first component, a first through hole and a first guiding structure, wherein the first through hole is formed in the lower end of the first component and communicates with the first groove. The second component is located in the first component, can slide up and down and is provided with a second component upper end, a second component lower end and a second through hole, wherein the second component upper end is in clearance fit with the first groove, the second component lower end is in clearance fit with the first through hole, the axis of the second through hole coincides with the axis of the first through hole, and the lower end face of the lower end of the second component is a horizontal plane. The third component is fixedly connected with the first component and is provided with a first ejector rod which is arranged on the lower surface of the third component and is in clearance fit with the second through hole. The fourth component is provided with a second ejector rod which is in clearance fit with the first through hole, a third through hole which is in clearance fit with the first ejector rod and a second guiding structure matched with the first guiding structure, and the upper end face of the second ejector rod is a horizontal plane. The inner diameter and the outer diameter of the gasket manufactured through the tool are concentric.