A facile hydrothermal route employing H2O2 as structure-directing agent was explored to fabricate anatase microflowers with dominant {101} facets and anatase rnicrospheres with exposed {001} facets. The influence of H2O2 concentration on crystal structure, morphology, and facet composition of TiO2 was investigated in detail. H2O2 plays a crucial role in determining the crystal structure, morphology, and exposed facets of TiO2. The presence of H2O2 favors the formation of anatase phase. When the concentration of H2O2 was in the range 0.7-3.3 M, anatase microflowers with dominant {101} facets were produced. In contrast, when the concentration of H2O2 was higher than 6.6 M, anatase microspheres with exposed {001} facets were formed. A mechanism was proposed to account for the influence of H2O2 on crystal structure and morphology of TiO2. Photocatalytic degradations of rhodamine B and 2,4-dichlorophenol indicated that anatase microspheres with exposed {001} facets showed much higher photocatalytic activity than anatase microflowers with dominant {101} facets.