The electrical, optical and structural properties of ZnNiO thin _ films deposited on Si substrates using rf-magnetron sputtering method have been investigated before and after the thermal annealing processes. The crystallinity of the ZnNiO thin film become degraded with increasing the Ni contents. This is mainly because the lattice of the thin film was expanded due to the oxygen-deficient conditions. Concerning the electrical properties of the thin film, the carrier concentration increases ($6.81 imes10^{14} extrm{cm}^{-2}$) and Hall mobility decreases (36.3 $ extrm{cm}^2$/Vㆍs) with higher doping concentration of Ni. However, the carrier concentration and Hall mobility became low ($1.10 imes10^{14} extrm{cm}^2$ and high (209.6 $ extrm{cm}^2$/Vㆍs), respectively, after the thermal annealing process at $1000 ^{circ}C$. We also observed a strong luminescene center peaking at 546 nm in photoluminescence spectra, which was caused by a deep level center in the ZnO band gap with oxygen deficient ZnNiO structure.