Zn_1-xCd_xO crystal thin films with different compositions were prepared on silicon and sapphire substrates by the dc reactive magnetron sputtering technique. X-ray diffraction measurements show that the Zn_1-xCd_xO films are of completely (002)-preferred orientation for x≤0.6. For x = 0.8, the film is a mixture of ZnO hexagonal wurtzite crystals and CdO cubic crystals. For pure CdO, it is highly (200) preferential-oriented. Photoluminescence spectrum measurement shows that the Zn_1-xCd_xO (x = 0.2) thin film has a redshift of 0.14 eV from that of ZnO reported previously.