The Bi2WO6 nanospheres were synthesized by hydrothermal method. The influences of different pH conditions on Bi2WO6 crystalline phase, morphology, pore distribution, chemical composition, optical proper and photocatalytic efficiency were researched. Characterization and catalytic results show that when the pH=1, the shapes of Bi2WO6 sample is a sphere with many dense voids inside.Then, with the pH getting higher, the interior of the Bi2WO6 aperture has become looser. When the pH=7, the Bi2WO6 nanospheres becomes flakes. The bandgap energy of Bi2WO6 synthesized at pH 1，3，5， 7 is 2.14~2.26 eV. The sequence of photo degradation of RhB from big to small is pH=7，pH=5，pH=3，pH=1, which is attributed to the strongest diffraction peak of Bi2WO6 under the condition of pH=7, complete crystal form, high crystallinity and RhB degradation rate.