Smart　supply　chain　services　rely　on　the　utilization　of　massive　amount　of　data　collected　by　sensor　networks　deployed　in　different　enterprises.　Sensing　as　a　Service　(S2aaS)　is　a　promising　Internet　of　Things　(IoT)　business　model　pattern　for　data　exchange.　The　current　centralized　IoT　S2aaS　models　are　not　suitable　for　IoT　big　data　exchange　due　to　the　issues　on　privacy　disclosure,　single　point　of　failure,　data　security,　performance,　etc.　In　this　paper,　we　propose　a　blockchain-based　decentralized　framework　for　IoT　S2aaS　for　smart　supply　chain,　which　can　ensure　the　IoT　solution　owners　have　full　control　of　their　data　and　securely　exchange　data　with　data　consumers　without　intermediaries.　We　introduce　the　system　model　and　the　layered　architecture　of　our　proposed　framework,　based　on　which　we　give　a　concrete　scheme,　smart　contract　is　used　to　perform　the　whole　process　of　IoT　S2aaS.　We　implement　a　software　prototype　on　Ethereum.　Experiment　results　show　the　validity　and　effectiveness　of　our　proposed　solution.　　©　2023　The　Authors.