Abstract: A model for estimating and predicting the optical turbulence in the surface layer over land is presented based on Monin-Obukhov similarity theory, and some numerical analyses are carried out in comparison with other models. It is found that under unstable conditions, the optical turbulence over land with flat terrain can be well estimated by using standard meteorological parameters and some experiential data. The estimated result shows that the model is in good agreement with the measurements. When wind speed is low, the turbulence intensity (represented by refractive-index structure constant) becomes weaker with the stronger wind. The optical turbulence of some day and year is predicted with the Thiermann-Kohnle model by using geographic information and solar irradiance regularity. Finally, the refractive-index structure constant and inner scale are estimated using meteorological data measured on the spot.