Two　kinds　of　bismuth　molybdates:　alpha-Bi2Mo3O12　nanotablet　and　gamma-Bi2MoO6　nanoplate　were　prepared　employing　mild　hydrothermal　methods.　By　tuning　the　n(Bi)/n(Mo)　ratio　and　pH　values,　controlled　formation　of　bismuth　molybdates　can　be　achieved.　Low　pH　value　and　high　concentration　of　molybdenum　lead　to　the　formation　of　alpha-Bi2Mo3O12.　High　pH　value　and　low　concentration　of　molybdenum　favor　the　formation　of　gamma-Bi2MoO6.　Photophysical　and　photocatalytic　studies　indicate　that　gamma-Bi2MoO6　nanoplate　shows　more　intense　absorption　band　in　the　visible　light　region　and　better　photocatalytic　activity　than　alpha-Bi2Mo3O12　nanotablet　under　visible　light　irradiation.　The　effect　of　factors　on　photocatalytic　activities　for　two　kinds　of　photocatalysts　was　also　discussed.