Internet　of　Things　(IoT)　plays　an　important　role　in　the　development　of　various　fields.　The　increasing　scale　and　scope　of　applications　make　a　great　demand　of　IoT　data　exchange　in　recent　years.　Meanwhile,　a　number　of　IoT　data　exchange　platforms　which　dedicated　to　connecting　various　and　distributed　data　sources　are　emerging.　In　such　a　platform,　service　providers　can　search　and　exchange　the　data　sets　that　they　need.　However,　the　centralized　infrastructure　cannot　provide　enough　trust　as　the　third-party　intermediaries　for　data　exchange.　As　a　result,　most　platforms　unable　to　satisfy　the　complex　requirements　due　to　few　institutions　and　individuals　are　willing　to　share　their　IoT　data　sets　in　such　an　untrustworthy　environment.　This　paper　proposes　a　decentralized　solution　based　on　the　blockchain　for　IoT　data　trusted　exchange.　Specifically,　In　this　paper,　the　basic　principles　of　blockchain　and　corresponding　key　technologies　are　expounded　through　in-depth　analysis　of　three　main　reliable　requirements　in　IoT　data　exchange.　Besides,　this　paper　provides　an　architecture　of　above　solution　and　detailed　design　of　its　main　trust　component.　Finally,　it　realizes　a　prototype　by　using　Ethereum　blockchain　and　smart　contracts　and　presents　its　auditable,　transparent,　decentralized　features　visually.　©　2017　IEEE.