Abstract: With a large number of nonlinear loads connected to the power grid, the harmonic problems caused by them are becoming more and more serious. Various countries or organizations have formulated harmonic standards to constrain the harmonic emission values of nonlinear users to ensure the waveform quality of the AC power grid. How to distribute the allowable harmonic emission value fairly and reasonably among power users has become a key issue. By comparing and analyzing the harmonic emission level distribution methods of nonlinear load access to high voltage system in IEC 61000-3-6, GB / T 14549 and IEEE Std.519, the applicability of each standard is evaluated by three principles of fairness, consistency and feasibility, and the consistency of the three is evaluated by comparing the case study results, which can provide some references for the revision of harmonic national standards.