The SrO/CeO2/ALG nanocomposite was successfully constructed by using the co-precipitation method and was analyzed with zeta potential, FTIR, SEM, XRD and BET techniques. A common Azo dye, namely Reactive Red 195, widely utilized in the dyeing industry and causing environmental pollution, was chosen to examine the photodegradation of SrO/CeO2/ALG nanocomposite, and it was shown that this dye could be successfully degraded by prepared nanocomposite. Impacts of factors such as pH, contact time and effect of different concentrations of dye and catalyst, the effect of scavengers and the effect of hydrogen peroxide were investigated to find out degradation efficiency. This SrO/CeO2/ALG nanocomposite was used for the photodegradation of reactive red 195 dye and 93% degradation efficiency was obtained at pH 3, 6 mg of catalyst concentration, dye concentration of 10 ppm, and contact time of 90 min. Degradation kinetic studies were determined by applying first-order and Langmuir-Hinshelwood reactions. The results exhibit a novel method for the synthesis of nanocomposite to effectively cause photodegradation of organic pollutants from wastewater and can be applied to industrial manufacture. The mesoporous SrO/CeO2/ALG nanocomposite also captured 4.31 and 2.98 mmol/g CO2 at 25 and 40 °C temperatures, respectively.