Oxygen vacancies (OVs) defective BiOCl nanosheets are important for developing efficient hole (h(+)) oxidation. Herein, a facile hydrolysis without the use of organic solvent was developed for preparing OVs-controllable BiOCl nanosheets, which was then applied to degrade perfluorooctanoic acid (PFOA), a typical persistent organic pollutant, which is resistance to the oxidation by hydroxyl radicals ((OH)-O-center dot). As changing the alkali source in the preparation process, the ratio of OVs in BiOCl nanosheets increases from 0.573 to 0.981, and the photocatalytic performance of BiOCl for the degradation and defluorination of PFOA increases by 3-4 times. A linear relationship between the photocatalytic degradation of PFOA and the OVs amount in BiOCl was observed. The introduction of OVs in BiOCl not only offers localized states for trapping photo-generated electrons, but also acts as active sites for adsorbing PFOA, both of which are helpful to improve the h(+)-oxidation of PFOA. The photocatalytic degradation of PFOA was more effective at pH 4.6 compared to other previously reported highly acidic and alkaline conditions. These factors ultimately guaranteed the improved degradation and defluorination of PFOA over OVs-rich BiOCl nanosheets. This work provides a readily achievable tactic to induce OVs formation on nanocrystals for enhanced photocatalytic water treatment.