The NiO/reduced graphene oxide (RGO) hybrid film has been prepared by a sol-gel method [1].The microstructures of the hybrid films were characterized by X-ray diffraction and scanning electron microscopy (SEM).The results show that NiO/RGO films transform from Ni(OH)2 into NiO at about 300 ℃.The SEM images indicate that the surfaces of the films have irregular cracks and the typical thickness is about 80 nm.The hybrid film exhibits electrochromism with reversible color changes from transparent to dark brown and the activation period varies with the annealing temperature [2].After 50 periods, the fully active sample prepared at 300 ℃ shows the variation of transmittance up to 66.1% at 550 nm.Hence, a simple method to prepare NiO/reduced graphene oxide hybrid films with good electrochromic performance was established and may be helpful in the industry product of electrochromic devices.