Harmonic governance is very important to power quality control. The traditional ip-iq method has problems such as low detection accuracy and slow speed. Therefore, it is proposed to increase the negative feedback loop based on quasi-proportional-resonance(QPR) filter based on the traditional second-order generalized integrator (SOGI), and replace the traditional PI link with the P link, and change the low-pass filtering link in the traditional ip-iq method to obtain an improved ip-iq harmonic current detection method. The simulation and experimental results show that the improved phase lock loop shows excellent frequency locking ability in the condition of abnormal power grid. In addition, through the improved ip-iq harmonic detection method, the current distortion rate of the fundamental wave current calculated by the algorithm can be significantly reduced, and the current distortion rate is reduced from 0.29% to 0.20%. And reduced from 8.63% to 0.51% in the presence of a DC component. At the same time, the harmonic can still be accurately detected in the complex power grid environment.