A simple and controllable solvothermal method was used to synthesis a series of BiOCl nanosheets with various surface oxygen vacancies (OVs) concentration. The introduction of OVs on surface BiOCl nanosheets broaden the photo-absorption to the visible-light-region, induce a remarkable photothermal effect, and enormously promote efficient charge separation. The OVs abundant BiOCl nanosheets exhibit an outstanding selective CO generation rate of 15.33 μmol·g−1·h−1 under the simulated sunlight irradiation, without any sacrificing regent, which is roughly 20.1 times higher than that of pure BiOCl nanosheets. For the degradation of Rhodamine B and tetracycline hydrochloride under visible light, the activity of OVs enriched BiOCl nanosheets is about 43 and 19.5 times higher than that of pure BiOCl nanosheets. The improved photocatalytic activity is attributed to the strong photothermal effect, the tuned electronic structure and the excellent visible light absorption induced by oxygen vacancies. Furthermore, the possible photocatalytic mechanisms, including the separation and transport of carriers, generation process of reactive species and degradation intermediates of tetracycline hydrochloride, are revealed in-depth. Hence, this work may pave the way to illustrate the function of oxygen vacancies in the semiconductor photocatalysis process.