NiO thin films with different annealing temperature and films thickness were fabricated by magnetron sputtering on the Pt/TiOx/SiO2/Si substrates. The XRD results show the crystallinity of films can be improved with the annealing temperature and films thickness increased. While the preferential orientation is affected by annealing temperature and films thickness. The SEM results show that the average size of the needle like grains shape increases gradually from 42.4 nm to 72.5 nm and the grains of films are seen to be more uniform, with a smoother and finer morphology with film thickness increasing. XPS measurements show that two valence states of Ni2+ and Ni3+ exist in NiO films with the Ni2+/Ni3+ ratio 1.01. However, the Ni3+ refers to the structure that contains Ni2+ ions with holes and not to Ni2O3 phase as observed from the XRD results and the 01 s XPS spectra, making the grains conducive due to plenty of holes. It results the grains have a key contribution to dielectric behavior. The frequency domain spectroscopy shows the films thickness and annealing temperature have a significance influence on the dielectric constant and dielectric loss tangent. And the preferential orientation of NiO films play a non-negligible impact on the dielectric performance due to the polarized NiO (111) plane.