Abstract: The harmonic pollution on the power grid depends not only on the generation of nonlinear thyristor-based converter load, but also on the amplification of harmonics throughout the reactive power compensation system. At present, the harmonic current amplification formula is often used for the conduction evaluation, but it is difficult to characterize the mechanism of the whole spectrum conduction. Based on the Parseval-Rayleigh energy theorem criterion, a harmonic coefficient algorithm for nonlinear load is proposed. The calculation example of harmonic coefficient for the nonlinear load by MATLAB is analysed, and the correctness is validated by comparing with the measured data in the EAST experiment.