A method of calculating theoretical power of wind farm based on extrapolation of anemometer tower data includes following steps. A number of anemometer towers in a wind farm is selected, and analyzing historical data acquired by the number of anemometer towers. An air density is calculated based on the historical data of the number of anemometer towers. A power curve is calibrated based on the historical data of the number of anemometer towers. The power curve is fit based on a wind speed and a wind power of a fan head of each wind turbine based on the historical data. An theoretical power calculation extrapolation model of anemometer tower data is constructed. Real-time anemometer tower wind data and a calibrated air density are inputted into the theoretical power calculation model and calculating the wind power. The theoretical power is obtained.