Bi-N-TiO2　nanoparticles　were　synthesized　via　anneal　after　a　simple　sol-gel　combined　hydrothermal　method.　X-ray　diffraction　(XRD),　UV-Visible　diffuse　reflectance　spectra,　Scanning　Electron　Microscope　(SEM)　and　X-ray　photoelectron　spectra　(XPS)　confirm　that　the　grain　sizes　are　almost　uniform　diameters　of　about　11　nm,　the　response　to　light　extends　to　visible　region,　the　doped　ions　substitute　some　of　the　lattice　titanium　atoms,　and　furthermore　Bi3+　and　Bi4+　ions　coexist.　The　photodegradation　of　acid　orange　7　(AO7)　is　used　to　evaluate　the　photocatalytic　activity　of　the　prepared　Bi-N-TiO2　nanoparticles.　The　experiments　indicated　that　Bi-N-TiO2　showed　higher　photocatalytic　activity　than　that　of　P25,　TiO2,　N-TiO2　and　Bi-TiO2　in　the　visible　light　area　and　ultraviolet　light.　The　improvement　of　photocatalytic　activity　of　Bi-N-TiO2　is　more　likely　because　the　N　doping　causes　the　visible　light　response　and　improves　the　quantum　yield　and　photocatalytic　activity　of　TiO2,　and　Bi　doping　causes　the　enhancement　of　the　separation　of　photogenerated　charges.