The load of ITER test platform is a superconducting coils which has large inductance, when it connected to the grid will produce large amounts of reactive power, resulting in grid voltage drop, affecting power quality. In order to detect the reactive power compensation effect of reactive power compensation and filtering devices, this paper achieves the calculation of reactive power by Hilbert algorithm and interpolation FFT algorithm of double spectral lines, then using data acquisition card and LabVIEW for realtime test data gathering, analysis and display. It verifies the validity of the two algorithms by comparing the results of power quality analyzer.