NiO films are prepared with radio frequency magnetron sputtering. Ellipsometric experiment results show that NiO film is transparent for visible light,and its refractive index can be modified by changing Tsub and annealing temperature. Scanning electron microscopy and X-ray diffraction experiment results show that Tsub and annealing temperature can modify the morphology and crystal structure of NiO film which can further modify the conductivity of NiO. The optimized NiO film is used in polymer solar cell (PSC) as an anode blocking layer. The experimental results show that NiO is a better candidate than the PEDOT:PSS often used as an anode blocking layer for PSC. The power conversion efficiency of PSC with NiO reaches 2.26% which is three times as high as that with PEDOT:PSS.