The spin Seebeck effect is a phenomenon of spin Seebeck voltage signal caused by temperature gradient in (sub) ferromagnet, which has become one of the hot research fields of thermal spintronics. In this paper, NiO thin films were deposited on Si substrates by reactive magnetron sputtering. The effects of sputtering power, oxygen-argon ratio, sputtering pressure and substrate temperature on the microstructure and surface morphology of NiO thin films were investigated. The optimum conditions of reactive magnetron sputtering are sputtering power 110 W, oxygen-argon ratio 0.15 (O2 15 mL/min; Ar 100 mL/min), sputtering pressure 0.3 Pa and substrate temperature 400 ℃. The effects of temperature gradient (temperature difference), magnetic field angle, NiO thickness and Pt thickness on spin Seebeck voltage in Si/NiO/Pt structure were studied. The results show that there is a simple linear relationship between the spin Seebeck voltage and the temperature difference, the larger of the temperature difference, the higher of the spin Seebeck voltage, and the relationship between the magnetic field angle and the spin Seebeck voltage satisfies the cosine function, that is, the spin Seebeck voltage is the maximum at 0° and 180°, and zero at 90° and 270°. The greater of the thickness of the antiferromagnetic insulating layer NiO, the stronger of the measured spin Seebeck voltage signal. The thicker of the paramagnetic metal layer Pt, the weaker of the spin Seebeck voltage signal.