At　present,　the　centralized　architecture　for　the　Internet　of　Things　(IoT)　data　management　faces　the　risks　of　data　leakage,　single-point　failure,　and　vulnerability　to　malicious　attacks.　Recently,　many　researchers　and　security　analysts　are　focusing　on　the　blockchain　technology　to　solve　the　security　and　privacy　issues　of　the　IoT　data　management.　However,　current　blockchain　technologies　are　unable　to　meet　the　highly　concurrent　IoT　data　transactions　and　the　fast　expansion　of　IoT　devices　due　to　the　decentralized　architecture.　Moreover,　there　is　a　lack　of　useful　solutions　for　effective　data　sharing　between　public　and　private　networks,　and　networks　with　different　services　(e.g.,　smart　grid　and　intelligent　transportation).　In　this　paper,　we　propose　a　decentralized　data　access　model　for　IoT　data　storage　and　sharing　based　on　the　FISCO-BCOS　blockchain.　In　the　model,　we　divide　the　IoT　devices　that　handle　different　services　into　different　set-chains.　These　set-chains　share　data　with　each　other　through　an　elaborate　access　control　model.　Experimental　results　show　that　the　proposed　model　fits　the　characteristics　of　the　IoT　data　management,　guaranteeing　the　privacy　and　security　requirements　with　better　scalability.　Our　model　can　be　used　as　a　solution　for　smart　cities.　©　2019,　Springer　Nature　Switzerland　AG.