An optical flow calculation method is proposed based on median absolute deviation (MAD) to estimate the refractive index structure constant of near-surface atmospheric turbulence, namely, Cn2. Specifically, this paper captures the jitter information of adjacent target images with multiple frames shot by a telescopic system through optical flow calculation and obtains the mean value of the angle-of-arrival fluctuation variance on the transmission path, so as to estimate the refractive index structure constant of near-surface atmospheric turbulence. Subsequently, a 6-day observation experiment is carried out in Hefei, and the mean value of Cn2 estimated by the model is comprehensively compared with the results measured by a micro-temperature sensor on the observation path. As a result, in terms of estimated and measured values, the mean deviation (BIAS), root-mean-square error (RMSE), and correlation coefficients are -0. 0202, 0. 2391, and 0. 8230, respectively. Therefore, it is fully proved that the proposed method can effectively estimate the refractive index structure constant of near-surface atmospheric turbulence and provide reference for the inversion of atmospheric turbulence parameters based on images.