(BixGa1-x)2O3　films　were　prepared　at　820　°C　by　sol-gel　method,　an　ethylene　glycol　solution　of　hydrated　gallium　nitrate　and　bismuth　nitrate　stabilized　by　monoethanolamine,　of　which　crystallization,　surface　morphology　and　electronic　structure　as　well　as　optical　properties　were　studied　in　detail　by　X-ray　diffraction,　Scanning　electron　microscope-energy　dispersive　spectrometer,　Fourier　transform　infrared　spectroscopy,　X-ray　photoelectron　spectroscopy　and　Ultraviolet-visible　spectroscopy.　XRD　showed　Ga2O3　film　prepared　from　solutions　consisted　of　two　crystal　structures,　β　and　γ,　increasing　Bi　atoms　into　Ga2O3　that　enable　the　inhibition　of　γ　phase　formation　and　(BixGa1-x)2O3　and　Ga2O3　capable　of　holding　the　same　monoclinic　crystal　structure.　EDS　displayed　(BixGa1-x)2O3　films　of　varied　compositions　were　obtained　with　content　of　different　Bi　atoms　into　the　solution,　which　kept　same　monoclinic　crystal　as　β-Ga2O3　when　Bi　ranged　from　0　<　x　<　0.056.　FTIR　revealed　that　the　absorption　band　below　480　cm−1　corresponded　to　the　octahedral　position　of　Ga2O3　and　the　Bi　atoms　in　the　(BixGa1-x)2O3　films　substituted　the　Ga　in　the　[GaO6]　octahedron.　XPS　exhibited　increasing　Bi　content　raised　Ga3+/Ga　ratio.　UV-VIS　provided　evidence　that　optical　band　gap　of　(BixGa1-x)2O3　down　to　3.2　eV　indicating　Bi-doping　achieved　Ga2O3　band　gap　tunable,　concurrently,　the　bowing　parameter　c　=　1.83　eV　was　obtained　on　the　basis　of　the　fitting　curve　of　band　gap.　[Figure　not　available:　see　fulltext.].　©　2022,　The　Author(s),　under　exclusive　licence　to　Springer　Science+Business　Media,　LLC,　part　of　Springer　Nature.