The utility model relates to a desulfurizing slurry return -flow system with pressure -relief device, including force (forcing) pump, thick liquid jar, sizing pipe way, backflow pipeline, slurry conveying pipe way, top jar, governing valve, by pass vavle, grout inlet pipeline, the force (forcing) pump says with grout inlet pipeline, thick liquid jar, sizing pipe and is connected that the thick liquid jar passes through the by pass vavle to be connected with backflow pipeline one end, and the backflow pipeline other end is connected with sizing pipe way, slurry conveying pipe way, the slurry conveying pipe way with push up the jar and be connected, be equipped with the governing valve on the slurry conveying pipe way, still include the release jar, the release jar is connected with sizing pipe way, slurry conveying pipe way, backflow pipeline. The advantage is: defeated slurry feeding hydraulic pressure force is unchangeable at a jar, and the backward flow thick liquid has reduced the by pass vavle pressurized through the laggard backflow pipeline of release jar release, has prolonged by pass vavle life, has protected the governing valve, realizes desulfurization system's more steady operation.