Ce1-xCoxO2-δ films with the stoichiometry of x=0,0.03,0.06,0.1,0.125 were fabricated on Si(111) substrates using O2 assisted pulse laser deposition method. While pure CeO2 film is weak paramagnetism, integration of low Co content of 3 at. % introduces ferromagnetim with a giant saturation moment (Ms) of 5μB/Co at room temperature. Based on the first principle calculation, we attribute the giant magnetic moments to the combined contributions of spin polarized Co, Ce, and O atom with the enhancement of O vacancies. Higher Co content will depress the ferromagnetism, i.e., inverse correlation between Ms and Co contents, which is qualitatively validated by the calculated magnetic moments of Ce1-xCoxO2-δ with different Co content.