To　reveal　the　origin　of　the　IoT,　evaluate　its　mainstream　research　topics,　and　discuss　the　challenges　facing　the　IoT　in　the　future,　this　paper　conducts　a　bibliometric　study　of　the　IoT　from　2000　to　2019.　First,　this　paper　presents　a　basic　bibliometric　overview　of　the　IoT.　Second,　co-citation,　coupling　and　cluster　analysis　methods　are　used　to　analyse　collaboration　networks,　and　VOSviewer　is　used　to　visualize　the　networks.　Third,　biblioshiny　is　used　to　analyse　the　thematic　trends　of　IoT.　Finally,　this　paper　discusses　IoT　challenges　and　provides　some　suggestions　to　address　them.　The　limitations　of　this　paper　are　also　summarized.　Research　results　show　that,　the　mainstream　studies　in　this　field　mainly　focus　on　IoT　security,　wireless　sensor　networks,　IoT　management,　IoT　challenges　and　privacy.　In　addition,　the　thematic　evolution　of　keywords　shows　that　security　and　algorithm　issues　have　become　basic　themes　in　the　field　of　IoT　research　in　recent　years.