High-performance thermochemical water splitting catalyst is the key in solar-driven H-2 production for the development of sustainable and clean energy technology. Perovskite oxides have been considered promising redox catalysts for two-step thermochemical H2O splitting cycles due to their remarkable oxygen exchange capacity at low thermal heating temperatures. This study is the first to investigate perovskite series of La1-x Ca (x) CoO3 for two-step thermochemical H2O splitting cycles. The Ca doping contents in La1-x Ca (x) CoO3 perovskites showed a significant effect on the O-2 and H-2 production performances. Increasing the Ca doping content has greatly increased O-2 evolution during the thermal reduction process. However, high Ca dopant content significantly weakened the reaction thermodynamics of the subsequent H2O splitting and led to lower re-oxidation yields. After tuning the Ca doping level from 0.2 to 0.8, La0.6Ca0.4CoO3 was identified as the best trade-off among the tested La1-x Ca (x) CoO3 perovskites. The thermal reduction and water splitting temperatures were also systematically investigated to optimize the thermochemical operational conditions. La0.6Ca0.4CoO3 showed maximum H-2 production of 587 A mu mol g(-1) when the two-step thermochemical H2O splitting carried out between 1300 and 900 A degrees C, eighteen times higher than that of CeO2 under the same experimental condition. More importantly, La0.6Ca0.4CoO3 also exhibited fairly good catalytic stability during the thermochemical cycling test and has strong potential for long-term applications.