The　current　casing　diameters　of　the　production　section　are　about　244　mm　in　marine　natural　gas　hydrate　(NGH)　tried　tests,　which　are　a　small　order　of　magnitude　and　have　the　great　potential　to　be　enlarged.　Expanding　the　contact　areas　between　the　wellbore　and　the　NGH　reservoir　using　complex　structure　wells　has　been　popularly　studied　recently.　In　this　study,　the　enlarged　wellbore　diameters　(casing　diameters)　of　complex　structure　wells　were　first　proposed　to　enhance　the　gas　recovery　from　the　NGH　reservoir　in　the　Shenhu　area　of　the　South　China　Sea.　The　gas　production　characteristics,　temperature,　and　pressure　in　the　NGH　reservoir　and　near　the　wellbore　induced　by　the　depressurization　method　were　analyzed　under　various　wellbore　diameters　of　complex　structure　wells.　Results　indicate　that　using　the　enlarged　wellbore　diameter　can　further　expand　the　contact　areas　between　the　wellbore　and　the　NGH　reservoir,　promoting　gas　production　efficiency,　especially　in　short-term　production.　The　evolutionary　trends　of　temperature　and　pressure　meet　the　conditions　for　stable　short-and　long-term　pro-duction.　Moreover,　it　was　suggested　that　a　relatively　significant　gas　production　increase　of　the　enlarged　wellbore　diameter　could　be　obtained　by　a　slight　increase　in　the　wellbore　diameter.