Abstract: It uses CFD software Meteodyn WT to analyze the power generation loss before and after the construction of a mountain wind farm.In the construction of the mountain wind farm project, the lifting platform reduces the altitude of the fan to cause different degrees, then the wind speed at the wheel hub, resulting in the loss of wind turbine power generation.The researches show that five wind turbines of the wind farm are affected by the lifting platform after construction.The altitude of the maximum and minimum altitude decreases by 11.40 m, 7.80 m, and 9.34 m on average.Under the influence of altitude reduction, at the hub of the wind turbine, the wind speed decreases by 0.030 m/s at the maximum, 0.010 m/s at the minimum, and 0.018 m/s on average.The power loss of the whole wind farm is 287.390 MWh/year, and the maximum power loss of a single wind turbine is 84.090 MWh/year and the minimum is 40.520 MWh/year.