Aiming at the problems of the single phase harmonic current detection method, analyzes the harmonic detection method without phase locked loop (PLL) and proposes an improved single-phase harmonic current detection method without PLL. The method combines low pass filter and mean filter in series form to optimize the original low-pass filter and improve the detection precision and dynamic response speed; and for further accelerating the dynamic response speed, the fundamental wave current feedback form is applied. Matlab/Simulink simulation results show that this method is feasible and greatly improves the detection accuracy and dynamic response speed.