The theoretical atmospheric refractivity model, which based on the standard atmosphere, fails to reflect the volatility of the actual atmospheric refractivity. To solve this problem, an atmospheric refractivity estimation method is proposed according to stellar light deflection. Firstly, based on the stellar observation data of optical satellite, the stellar light deflected by atmospheric refraction is analyzed. An optical path model of which stellar light enters the optical satellite sensor after being refracted by the atmosphere is established. The symmetry of the optical path model is proved under the assumption of layered spherical atmosphere. Secondly, an iterative forward feedback method is proposed by measuring stellar light and theoretical stellar light, which can estimate the layered atmospheric refractivity. Finally, the method is validated using the stellar observation data. The calculated atmospheric refractivity agrees with the theoretical one, and shows the short-term volatility. The results of the experimental data show that more than 88% of the estimation error between the theoretical sight and the measured one is within 1%, and the remaining is no more than 20%.