The invention discloses a reinforced seepage-proofing structure for a pressure diversion tunnel. The reinforced seepage-proofing structure comprises a primary lining concrete layer, a reinforced seepage-proofing layer, grout stopping rings and a grouting layer, wherein the reinforced seepage-proofing layer is arranged on the primary lining concrete layer; the grout stopping rings are arranged between the primary lining concrete layer and the reinforced seepage-proofing layer, and divide a space between the primary lining concrete layer and the reinforced seepage-proofing layer into a plurality of grouting areas; the grouting layer is filled in the grouting areas enclosed by the primary lining concrete layer, the reinforced seepage-proofing layer and the grout stopping rings. The reinforced seepage-proofing structure has the beneficial effects that after reinforced seepage-proofing, a water passing section of a pressure diversion tunnel with a smaller tunnel diameter, for example, within a range of 3 to 5m, is reduced only by 2 to 3 percent and even less in case of wider and more longitudinal cracks, great seepage, serious reinforcement corrosion or the like; in addition, the reinforced seepage-proofing structure is simple in structure and high in safety, and has higher practical value for constructed pressure diversion tunnels, and steps of a construction method for the reinforced seepage-proofing structure are reasonable.