The mesoscale Weather Research and Forecasting (WRF) model coupled with wind farm parameterization is newly developed to simulate the wake flow and power production of a real onshore wind farm. First, wind farm flow field simulations are conducted with 1000 m, 500 m and 200 m horizontal resolutions, and the simulation results capture the wind farm observed data well. in addition, wind farm flow characteristics, power output, and influence on the atmosphere boundary layer (ABL) are resolved at a horizontal resolution of 200 m. The wake interactions, wind speed, and power output deficit in the wind farm are analyzed. The power comparison results prove that the proposed method can be applied to simulate the power output of a real onshore wind farm with high accuracy in real time. The influence of the wind farm on the ABL is also discussed. The results show that wind farm effects on the ABL occur mainly within the turbine rotor-spanned heights and the downstream regions behind the wind farm within 10 km, within which the speed deficit ratio can exceed 10%. For the region that is 18 km downstream of the wind farm, the average speed deficit ratio is only about 2%. This study is the first attempt to reproduce the wake flow and power output of a real onshore wind farm by the WRF model at such high resolution.