Abstract: In order to reduce the error of measuring PWHD (Partial Weighted Harmonic Distortion), Hanning windowed interpolation harmonic algorithm, 4 order Blackman-Harris windowed interpolation harmonic algorithm and Nuttall windowed interpolation harmonic algorithm were used to measure PWHD. The principle of the three algorithms were introduced, accuracy influence of sampling points and sampling frequency were compared. Based on GB15579.10 arc welding equipment electromagnetic compatibility requirements, this article analyzed the influence sampling points and sampling frequency to the welding power source’s PWHD under different window functions through experiment. The experiment results show that the higher accuracy PWHD value cannot be obtained by using Hanning windowed interpolation algorithm, while the higher accuracy PWHD value can be obtained by using 4 order Blackman-Harris windowed interpolation algorithm or Nuttall windowed interpolation algorithm and the performance of Nuttall windowed interpolation algorithm is the best.