The invention discloses a method and a mold for manufacturing a reflecting surface of a microwave antenna. The method includes forming a curved surface of a workpiece, flanging the flat side, and stretching the vertical side. By the secondary forming method, the defect of frequent breakage at the joint of the curved surface and the front flange is completely overcome. Further, the invention provides the manufacturing mold according to the manufacturing method, and the mold is simple in structure and easy to manufacture. In the actual production by using the mold, forming difficulty in forming the reflecting surface of the microwave antenna is greatly reduced, forming accuracy of products is improved, and draping at the edge of the reflecting surface is effectively prevented with a pressure ring. Via test, root-mean-square value delta of the reflecting surface of the microwave antenna 0.7 meters thick is up to 0.24 mm. In conclusion, operation is convenient, batch production of the reflecting surface of the microwave antenna can be realized, and popularization is facilitated.