Solar selective absorption coating is the core material of solar thermal utilization. A TiN/TiNO/SiO2 solar selective absorption coating was deposited by magnetron sputtering. The refractive index (n) and extinction coefficient (k) of infrared reflector layer TiN and absorption layer TiNO were determined, while the optical constants of anti-reflector layer SiO2 were reported in the literature. The ellipsometer angle (Ψ, Δ) was measured by ellipsometer and studied by W-VASE analysis and fitting software. The Tauc-Lorentz model in terms of infrared reflector layer TiN was established for data iteration and optimization and fitting, and the Drude model in terms of absorption layer TiNO was established for data iteration and optimization and fitting. The refractive index decreased from the infrared reflector to the anti-reflector, and the gradient structure reduced the surface reflection, which conformed to the design of optical interference coating. Optimization parameters in which continuous target reflectance was lower than 5% in the range of 300-1 500 nm were set by TFCalc software. The reflectance curve optimized by the software and the optimal thickness of each layer were obtained, and the optimized process parameters were determined. The reflectance curve optimized by the software and the reflectance curve of prepared coating were basically consistent in the wavelength range of 400-1 500 nm, and the experimental curve increased rapidly in the wavelength range of 1 500-2 500 nm. The optical properties and thermal stability of the coating were optimized by UV-VIS-NIR, FTIR, SEM, EDS, XRD and XPS. The absorptivity and emissivity of the optimized coating were 0.906 and 0.085 2 respectively, which were consistent with the optimized results. After heat treatment at 265 ℃ for 600 h, the absorptivity and emissivity of the coating were 0.933 and 0.103 3, respectively, and the PC value was less than 0.01. The surface composition of the coating did not change before and after heat treatment. The content of oxygen element increased slightly, indicating that the coating was not oxidized, showing a good oxidation resistance. No defects such as grain boundaries and cracks were observed, which was conducive to preventing the diffusion of oxygen atoms to the internal coating. There was a small increase about absorptivity with the increase of heat treatment time, while there was not a similar pattern about emissivity. This was related to the fact that the surface SiO2 oxide film layer prevented the grain growth to a certain extent. After heat treatment, a small number of pits were found locally on the surface of the coating, but the surface composition of the coating was almost unchanged. Further analysis showed that the recrystallization of SiO2 and TiO2 in amorphous matrix was the main reason for the improvement of absorptivity, and the elimination of residual stress during crystallization also contributed to the improvement of absorption efficiency. The surface of the coating after heat treatment is very dense, and the reduction of roughness is conducive to preventing the diffusion of oxygen atoms to the inner layer, which can effectively improve the thermal stability of the coating. The selective absorption performance and thermal stability of the optimized TiN/TiNO/SiO2 coating have been effectively improved, which is conducive to a strong practical application prospect.