Zn1-xCoxO (x=0.01, 0.02) dilute magnetic semiconductor thin films deposited on Si (001) substrates at 650℃ by pulsed laser deposition method were studied by X-ray absorption fine structure, X-ray diffraction and magnetic measurement. The typical ferromagnetic hysteresis curves were obtained by superconducting quantum interference device magnetometry at room temperature. The X-ray diffraction results showed that Zn1-xCoxO films were of the wurtzite structure. The X-ray absorption fine structure results revealed that the Co atoms were incorporated into the ZnO lattice and located at the substitutional Zn sites, and a homogeneous phase of Zn1-xCoxO was formed. Comparing the experimental curves with the theoretical calculation results, the additional peak C was assigned to the oxygen vacancies, which indicated that the ferromagnetism of Zn1-xCoxO films was strongly correlated with the existence of oxygen vacancies.