Ternary Zn 1 - x Cd x O (0=<x=<0.53) alloy crystalline films with highly (002)-preferred orientations have been prepared on glass substrates by using the dc reactive magnetron sputtering method and exposed to annealing treatments in O 2 ambient. The crystal quality of the annealed Zn 1 - x Cd x O films improves much. As a case of the sample with x=0.53, the diffraction peaks in intensity attain maximum values at the annealing temperature of 500 o C. But for the samples with x>=0.53, the CdO phase separation and re-evaporation from the films are very serious. So for the Zn 1 - x Cd x O films with higher Cd content, to prevent the segregation of CdO, the annealing temperature should be less than 400 o C, and the annealing time should be less than 1h.