Nanoplates　of　α-SnWO4　and　SnW3O9　were　selectively　synthesized　in　large　scale　via　a　facile　hydrothermal　reaction　method.　The　final　products　obtained　were　dependent　on　the　reaction　pH　and　the　molar　ratio　of　W6+　to　Sn2+　in　the　precursors.　The　as-prepared　nanoplates　of　α-SnWO4　and　SnW3O9　were　characterized　by　X-ray　powder　diffraction　(XRD),　N2-sorption　BET　surface　area,　transmission　electron　microscopy　(TEM),　high-resolution　transmission　electron　microscopy　(HRTEM)　and　X-ray　photoelectron　spectroscopy　(XPS).　The　XPS　results　showed　that　Sn　exists　in　divalent　form　(Sn2+)　in　SnW3O9　as　well　as　in　α-SnWO4.　The　gas-sensing　performances　of　the　as-prepared　α-SnWO4　and　SnW3O9　toward　H2S　and　H2　were　investigated.　The　hydrothermal　prepared　α-SnWO4　showed　higher　response　toward　H2　than　that　prepared　via　a　solid-state　reaction　due　to　the　high　specific　surface　area.　The　gas-sensing　property　toward　H2S　as　well　as　H2　over　SnW3O9　was　for　the　first　time　reported.　As　compared　to　α-SnWO4,　SnW3O9　exhibits　higher　response　toward　H2S　and　its　higher　response　can　be　well　explained　by　the　existence　of　the　multivalent　W　(W6+/W4+)　in　SnW3O9.　©　2009　Elsevier　B.V.　All　rights　reserved.