Abstract: Since its promulgation and implementation, GB/T 14549 has effectively regulated the harmonic issues in power grids and ensured the power quality. However, with the development of new power systems, the harmonics in power grids have exhibited new characteristics, making GB/T 14549 hardly fully adaptable to the current needs of power grid development and modern management. Therefore, aiming at the harmonic characteristics in new power systems, and based on allocation method for allowable harmonic current values specified in GB/T 14549, this paper focuses on the constraint index for total harmonic current, the selection method for power supply capacity, and the superposition method, respectively, and proposes the selection methods for key parameters. Its rationality and effectiveness are validated through the case studies, which effectively restricts harmonic injection and provides a reference for the revision of the national harmonic standards.