p-block metal composite oxides Sr_1.36Sb₂O₆ and Sr₂Sb₂O₇ synthesized by a hydrothermal method as photocatalysts in the degradation of tetracycline hydrochloride under UV light irradiation have been extensively studied. The effects of synthesis conditions on the photocatalytic activity were discussed. The Sr_1.36Sb₂O₆-100 °C-24 h-5 and Sr₂Sb₂O₇-150°C-24 h-2 samples prepared under optimal conditions exhibited remarkably different photocatalytic activities. The essential factors influencing the difference of photocatalytic performance were revealed. The results showed that the different photocatalytic activities observed for Sr_1.36Sb₂O₆ and Sr₂Sb₂O₇ could be attributed to their different electronic and crystal structures. Our work will provide a new perspective for the screening and design of p-block metal composite oxide photocatalysts to enhance the removal of organic pollutants in the environment.