Abstract: To sustain casing pressure in shale gas wells, a flocculent elastic material DeForm with the function like rebar in concrete was developed with the goal of improving the long-term sealing integrity of the cement sheath. Using DeForm as the basis of its chemical composition, an anti-deformation cement slurry under alternative loading suitable for large scale staged fracturing in shale gas well was prepared. The indoor performance evaluation results demonstrated that the system has excellent elastic toughness and durability, which can effectively improve the ability of cement sheath to resist alternative loading, to bring about synchronous deformation of casing and cement sheath and to ensure the long-term sealing integrity of wellbore. This cement slurry system has been successfully applied in 9 wells in the Fuling Shale Gas Field, with excellent cement job rating 88.9% and no sustained pressure in casing annulus. With such remarkable application results, the cement slurry will provide a new way in preventing sustained casing pressure in shale gas wells.