When using horizontal wells to develop bottom water reservoirs, predicting the production and water breakthrough time frame of different parts of the horizontal section before production, and predicting the bottom water coning after production are important issues to optimize the production system of horizontal wells. Based on the theory of stable seepage, this paper comprehensively considers the influencing factors such as the change of reservoir physical properties, permeability anisotropy, wellbore flowing pressure drop from horizontal toe to heel, and the uneven wellbore trajectory, establishes the mathematical model of fluid migration in bottom water reservoir, and then obtains the method to calculate the water breakthrough time frame at different parts of horizontal section of horizontal well. This method is used to predict the production and water breakthrough time in the horizontal section of an open hole completion horizontal well, which is in good agreement with the actual production results. The calculated bottom water coning is consistent with the law observed by physical simulation experiment, which shows that this method has strong practicability and high accuracy, and can provide reference for the optimization of horizontal well completion scheme and production system.