La_0.7–Sr_0.3–Co–O nano-composite shows stable and improved low-temperature activity for CO oxidation, with temperatures for ignition and full CO oxidation of 70 and 174 °C, respectively. Benefitting from the perovskite component, the catalyst shows stable activity during the reaction without appreciable loss after 36 h. Together with the characteristic results from XRD, XPS and TEM, it is inferred that the high activity of La_0.7–Sr_0.3–Co–O is attributed to its nano-sized structure, optimized Sr substitution, and especially a phase cooperation effect between the perovskite and metal oxides.