This paper studies and analyzes the special power-quality measurement results of a commercial onshore wind farm connected to the power grid of Taiwan Power System when Typhoon Matmo passed through Taiwan. This Kuan-Yuan onshore wind farm of 28.5 MW with nineteen 1.5-MW wind-turbine generator (WTGs) based on doubly-fed induction generator (DFIG) is connected to Kuan-Yin primary substation through two of four step-up main transformers of 161/69 kV, 200 MVA. The measured data were recorded from July 22, 2014 to July 29, 2014 for total 7 days. During the measurement period, Typhoon Matmo just passed through Taiwan and the nineteen WTGs were forced to stop. Special operating characteristics of the studied Kuan-Yuan wind farm subject to Typhoon Matmo were also recorded and studied. According to the measured results, the power quality of the studied Kuan-Yuan onshore wind farm during the measurement period can meet the grid code of Taiwan Power Company (TPC) except the voltage flicker of ΔV10. The time and date of the measured reactive power, maximum voltage variation, maximum voltage flicker, and maximum total demand distortion of current of the studied onshore wind farm related to the time and date of Typhoon Matmo are also discussed.