Ternary Zn1-xCdx O alloying films were deposited on silicon substrates by a reactive magnetron sputtering method.The structures of the films were characterized by transmission electron microscopy(TEM) and X-ray diffraction (XRD) analysis, respectively. The XRD measurement shows that the wurtzite-type structure of Zn1-xCdxO can be stabilized up to Cd content of x=0.53 without a cubic CdO phase separation.The TEM measurement shows that the films have a columnar structure and the grains are highly c-axis oriented perpendicularly on silicon substrate although some grain boundaries are slightly tilted.High resolution TEM observation indicates that a native layer of amorphous SiO2 exists at the ZnCdO/Si interface and that ZnCdO grains with c-axis preferred orientation nucleate directly on substrate surface.