More and more developers are asking for post-assessment work. The power generation index of wind turbines is one of the important indicators in the post-evaluation process of wind farm operation. Since the amount of electricity generated is closely related to wind energy resources, and wind energy is randomly variable and unpredictable, it is difficult to evaluate the power generation index. There are several main reasons for the deviation before and after the power generation: (1) Wind tower. If the wind tower used in the feasibility study stage is not representative, the wind measurement period is different, the wind instrument is aging, and the calibration is uncalibrated, the accuracy of the wind data will be affected, thus affecting the power generation. The feasibility study period to the actual operation takes at least 1 to 3 years, so the wind measurement period and instrument problems cannot be eliminated. (2) Model. If the model recommended in the feasibility study stage is not the wind turbine model determined by the owner, the power curve of each model will have a direct impact on the power generation result. (3) Fan layout. The fan layout of the feasibility study stage is based on the point optimization software. After proper adjustment and consideration of the safety distance with villages, roads, rivers, lines, etc., the wake is controlled below 8%; the actual operation stage The fan layout is in the micro-site selection stage, and each position is inspected to calculate the power generation, and the final position obtained in accordance with the site situation is obtained. The difference in fan placement has a direct impact on the results of power generation. Since there is a sequence before and after the feasibility study and the actual operation phase, the difference between the power generation caused by the fan layout cannot be eliminated. (4) Stop. Wind turbines in wind farms will have a direct impact on power generation if they are shut down due to faults, special weather conditions, force majeure, reasonable routine maintenance time, and misoperation shutdown. (5) Abandon the wind. At present, due to the relative lag of power grid construction, the load-limiting phenomenon of wind farms in many regions is more serious, and the wind-induced winds have a direct impact on power generation. (6) Software calculation accuracy. The industry's recognized power generation calculation software flat terrain is WAsP, and the complex terrain is CFD software. The accuracy of software calculation will have certain influence on the power generation result. This difference cannot be eliminated. (7) Selection of the reduction factor. The theoretical power generation of each fan calculated by the software in the feasibility study stage, after various reductions, the value of the on-grid power generation. The selection of the reduction factor has a direct impact on the value of the on-grid power generation.