Ce1Mn3 precursor was prepared by co precipitation method using cerium nitrate and manganese nitrate as raw materials, NaOH as precipitant. The composite metal oxide catalyst Ce1Mn3-x/γ-Al2O3 was prepared by mixing and calcining with nano alumina gel powder. X is the mass of Ce1Mn3 precursor powder (g), with values of 1, 3, 5, 7, and 9, and a total raw material mass of 10 g. The catalyst was characterized by XRD, BET and SEM, and its catalytic degradation performance on gaseous low concentration ethyl acetate (volume fraction 1000 ppm) was investigated by a fixed bed reactor. The effect of water vapor on the reaction and 48 hour catalytic stability were also explored. Compared with Ce1Mn3, the specific surface area of Ce1Mn3-x/γ-Al2O3 increases from 38.55 m2/g to 60.03~20.79 m2/g, and the number of mesopores significantly increases. Ce1Mn3 oxide is bound to the surface of γ-Al2O3, and the exposed Ce1Mn3 oxide particles have a finer and more dispersed morphology. When the mass ratio of Ce1Mn3 to alumina sol dry powder is 7:3, Ce1Mn3-7/γ-Al2O3 has the highest catalytic activity. Under the condition of space velocity (GHSV) of 15000 mL/(g·h), the degradation rate of ethyl acetate reaches 90% at 164 ℃ (T90). Both the carrier γ-Al2O3 and the addition of water vapor are beneficial for the degradation of ethyl acetate at low temperatures (<120 ℃), promoting the generation of degradation intermediates acetic acid and ethanol, resulting in a decrease in the final T90. In a reaction atmosphere test at 180 ℃ for 48 hours without water vapor, the Ce1Mn3-7/γ-Al2O3 catalyst can consistently maintain a degradation rate of over 99% for ethyl acetate.