Abstract: A series of La-Co composite oxides were prepared via co-precipitation method, and were characterized by N₂ adsorption&desorption, X-ray diffraction, scanning electron microscopy, Transmission electron microscope, H₂ temperature programmed reduction and X-ray photoelectron spectroscopy, respectively. Furthermore, the theoretical model of La-Co composite oxides were simulated using Density Function Theory (DFT). And then, the catalytic activity of the catalysts for degradation of 0.18% n-heptane and 0.18% toluene was respectively investigated in a continuous fixed bed reactor with GHSV of 15 000 h^-1, oxygen concentration of 10% and temperature from 150 to 275 ℃. The results showed that lanthanum significantly improves the physical and chemical properties of Co catalysts. It was observed that specific surface area is increased by 6 times, crystal space is reduced by 24 nm, and the energy required to adsorb oxygen is reduced by 0.62 eV. The catalyst named LCC4 performed best activity and obtained 90% conversion of n-heptane and toluene at 152 and 178 ℃, which dropped by 69 and 32 ℃ compared with that of the Co catalysts. Finally, the stability test of LCC4 catalyst was carried out over 500 minutes, and the loss of degradation activity of n-heptane and toluene was only 0.5%.