There are problems of sampling in multiple signal periods, with high complexity and uneven harmonic leakage distribution in the quasi-synchronous windowing analysis method of the power harmonic. Thus a fast and accurate power harmonic analysis method suitable for MCU is proposed using quasi-uniform sampling. The time discrete error of quasi-uniform sampling does not accumulate with continuous sampling, so two integer power synchronous sampling points can be obtained in one signal cycle, and harmonic analysis can be realized directly with the help of a FFT algorithm. Based on the fundamental component approximation of the signal and assuming that the time discrete and amplitude quantization errors of signal sampling obey a uniform distribution, the power harmonic estimation error using quasi-uniform sampling is analyzed. The algorithm and specific implementation process of power harmonic analysis are given. In the process, the sampling time is accurately controlled by long integer variables, and the algorithm is simple and efficient. Finally, the quasi-uniform sampling harmonic analysis algorithm is simulated. The results show that fast and accurate power harmonic analysis can be realized based on a general purpose MCU. This work is supported by the National Natural Science Foundation of China (No. 61871387).