Since energy transfer to oxygen species is generally considered to be the critical step during the O-2(center dot-)-driven photocatalytic reaction, it is important to develop approaches to design the oxygen defects induced photo catalysts to improve the performance of oxygen chemisorption. Here we report that a new strategy of oxide defect controlled MSnO3 catalyst is served to turn light into chemical energy by improving species chemisorption on the surface. CaSnO3 with the Ca/Sn ratio of 2.7 (2.7-CaSnO3) rich in oxygen vacancies exhibited a high photocurrent performance and an efficient photocatalytic activity. A superior photo efficiency is achieved for 2.7-CaSnO3, which reduces 93.9% MB dyes within 30 min under 100 mW/cm(2) white LED light irradiation, approximately 3.2 times larger than its stoichiometric one. Under the same LED light irradiation, 577.4 mu mol h(-1) g(-1) of H-2 and 62.0 mu mol h(-1) g(-1) of O-2 are realized over 2.7-CaSnO3. The chemisorption improved by oxygen defects in 2.7-CaSnO3 enables the transfer of photogenerated electrons to oxygen species in space. Therefore, oxygen molecules are activated into superoxide radicals on the oxygen defect-rich MSnO3 successfully. After more oxygen defects doping, the hydrogen evolution rate increases from 553.3 to 1152.7 mu mol h(-1) g(-1), while O-2 production rates increases from 62.0 to 129.1 mu mol h(-1) g(-1). The hydrogen reduction treatment further revealed that the enhancement of both hydrogen and oxygen evolution was realized by introducing more oxygen vacancies into 2.7-CaSnO3.