Synthesis of a novel biodegradable hydro soluble graft-copolymer named KGM-g-AM-g-AA-g-APEG was carried out using konjac glucomannan, acrylamide, acrylic acid, and allyl polyoxyethylene ether via free-radical copolymerization. Effective characterization methods, including XRD, TGA, FT-IR, H-1 NMR, and SEM, were adopted to evaluate the graft-copolymer. The good biodegradability of the graft-copolymer was confirmed, with a degradation rate >60% in 28 days, by a biological degradation experiment. Subsequently, it was found that the graft-copolymer showed superior shear resistance, shear reversible performance, temperature resistance, viscoelasticity, and salt tolerance compared with partially hydrolyzed polyacrylamide under the same conditions through rheological experiments. What's more, RE (14.1) and REF (4.95) of the graft-copolymer provided a valuable proof of the capability of mobility control and the great flooding effect with enhancing oil recovery by 13.76% in the presence of 6700 mg/L salt solution at 65 degrees C according to the core flooding tests.