In the power system with wind farms, the uncertain parameters that affect the economic operation of the system often have the characteristics of random fluctuation, which is easy to cause information loss in the process of power flow optimization. In this paper, the wind speed and load of wind farm are taken as the research object, and the probability box theory is used to describe the uncertainty of wind farm parameters. Firstly, the probability box model of wind and load is established by using the drift interval of distribution function. Then the probability box equal reliability discretization is introduced into the optimization model with the minimum generation cost as the objective function, and the optimal power flow model based on probability box theory is constructed. Finally, the interior point method is used to solve the model to obtain the optimal power flow calculation results, and the effectiveness of the proposed method is verified by comparing with the Monte Carlo method. The calculation results of IEEE30 bus system show that the probability box method can not only describe the uncertainty of the system more comprehensively and solve the optimal power flow problem effectively, but also shorten the calculation time and make the operation more simple and effective.