To realize the requirement of refined detection and compensation of fundamental and arbitrary harmonics in complex power grid environment, a new multi-functional refined detection method for fundamental and arbitrary harmonics is designed based on the traditional ip-iq detection method. Based on the instantaneous reactive power theory, the definition of the active/reactive component of harmonic current is given. The frequency signals of the specified harmonics are obtained by using a single phase-locked loop combined with frequency multiplier. The Park transform matrix of the traditional ip-iq method is improved by using the phase synthesis compensation method, and the DC component integral extraction method is designed to replace the low-pass filter in the traditional method. This method makes up for the lack of functionality of traditional detection methods, and has higher detection speed and accuracy. The effectiveness and flexibility of the proposed method are verified by MATLAB/Simulink simulation.