A method of forming a sealing structure for a bonded wafer is provided. The method includes providing the lower wafer and the upper wafer, forming a sealing material layer on each of the lower wafer and the upper wafer, forming a mask layer on the sealing material layer on each of the lower wafer and the upper wafer, etching the sealing material layer using the mask layer as an etch mask, so as to form a first protrusion at an edge of the lower wafer and a second protrusion at an edge of the upper wafer, and bonding the first protrusion and the second protrusion together to form the sealing structure. The sealing structure encloses a gap between the lower wafer and the upper wafer at an edge of the bonded wafer, so as to form a hermetically sealed cavity at the edge of the bonded wafer.