Abstract: For problems of large calculation amount, complex vector conversion, poor real-time performance and weak robustness of common harmonic detection methods based on instantaneous reactive power, a new ip-iq detection method without phase-locked loop was presented which was based on feedback and high-performance low pass filter. In the method, frequency of transformation matrix is preset to detect harmonic and fundamental currents without coordinate conversion and phase-locked loop. Fundamental current feedback is used for reducing detection error and dynamic response time. A high-performance low pass filter is realized by cascading low pass filter and mean filter, which can improve detection accuracy and response speed. The method can be applied to detect harmonic and fundamental currents in single-phase circuit, three-phase three-wire mode power system and three-phase four-wire mode power system.