This work prepared an anatase TiO2 by controlling coexposed {101} and {001} facets. The anatase TiO2 was composited with MoS2, and the photocatalytic behavior was studied. The relationship between the exposed ratio of {001} facets and the enhancement proportion by the composite was compared. An appropriate exposed ratio of {001} facets, instead of a high ratio, can cause the highest enhancement proportion for photocatalytic activity. This finding confirmed that exposed {001} facets are not the main factors for improving photocatalytic activity. Dual heterojunction was observed to form between MoS2 and anatase TiO2 with coexposed {101} and {001} facets, which is a crystal-face heterojunction between {101} and {001} facets and a semiconductor heterojunction between MoS2 and {001} facets of TiO2. In this dual heterojunction, photo-induced electrons in TiO2 will flow into {101} facets of TiO2, instead of MoS2, whereas the photo-induced holes in TiO2 will flow into MoS2 to reach a high separation efficiency. This finding further revealed the elevating mechanism of constructing heterojunction based on coexposed crystal faces.