Nowdays,　cloud　storage　technology　has　become　a　hot　topic,　and　an　increasing　number　of　users　are　concerned　with　the　security　of　their　data　in　the　cloud.　Many　auditing　schemes　on　the　cloud　are　proposed　and　the　introduction　of　a　third-party　auditor　to　assist　users　in　verifying　the　integrity　of　cloud　data.　As　a　centralized　node,　the　third-party　auditor　has　to　communicate　with　all　cloud　users　and　cloud　service　providers,　which　becomes　the　bottleneck　of　the　whole　scheme.　To　solve　this　problem,　we　design　a　blockchain-based　flexible　cloud　data　auditing　scheme.　In　our　scheme,　a　decentralized　auditing　framework　is　proposed　to　eliminate　the　dependency　on　the　third-party　auditor,　which　increases　the　stability,　security　and　performance　of　the　whole　scheme.　Since　the　cloud　service　provider　can　automatically　generates　auditing　proofs,　our　scheme　can　relieve　the　communication　burdens　of　the　cloud　service　provider.　The　proposed　scheme　also　adapts　the　Merkle　Hash　tree　to　improve　the　verification　performance.　Security　analysis　and　experiments　show　that　the　proposed　scheme　is　secure　and　has　better　stability　and　verification　efficiency.