The　structural　characteristic　and　electronic　properties　of　seven　WO3　bulk　poly　morphs　have　been　studied　by　first-principles　density　functional　theory　(DFT)　calculations.　Our　calculation　results　indicate　that　according　to　the　energy　of　WO3　per　unit,　the　stability　of　different　WO3　systems　reduces　in　turn　in　the　following　order:　monoclinic　WO3,　orthorhombic　WO3,　tetragonal　WO3,　triclinic　WO3,　hexagonal　WO3　and　cubic　WO3.　And　when　the　unit　cell　is　distorted　from　the　cubic　framework,　the　alternatively　long　and　short　W-O　bonds　are　formed,　implying　an　improvement　of　bonding-antibonding　splitting　associated　with　the　interactions　between　W　and　O　atoms.　The　deformation　of　the　WO6　octahedron　enhances　the　stability　of　the　system　to　some　extent　though　the　energy　difference　between　various　WO3　phases　is　small　(＜　0.1　eV/per　WO3　unit).　Besides,　the　band　gap　tends　to　enlarge　accompanied　with　the　symmetry　decrease　of　WO3　bulk.　According　to　the　band　structures,　the　minimum　band　gaps　for　those　WO3　polymorphs　are　direct　at　the　F　point　except　for　the　simple　cubic　and　hexagonal　structures.　In　addition,　for　all　the　WO3　phases,　the　compositions　of　the　valance　band　maximum　(VBM)　and　conduction　band　minimum　(CBM)　are　the　same,　which　are　relative　to　the　0　2p　and　W　5d　orbitals,　respectively.