It is an effective way to enhance the photocatalytic activity by fabricating some defects such as oxygen vacancy into WO ₃ lattice to make nonstoichiometric WO _3-x. This paper firstly describes the mechanism of the effect of oxygen vacancy on the photocatalytic activity of WO ₃, and then, reviews the influence of the localized surface plasmon resonance (LSPR) effect and the synergistic effects of noble metal/carbon containing materials, and oxygen vacancy. Finally, prospectsing and challenging of WO3-x application in the field of photocatalysis are discussed in the end of this work.