This document discusses harmonic estimation using the sliding window least mean square (SW-LMS) algorithm. It introduces harmonics and their effects, as well as traditional Fourier transform and LMS algorithms for analysis. The SW-LMS algorithm is presented as improving on LMS by using a sliding window to exclude oscillations and work better in noisy signals. Simulation results show the SW-LMS algorithm can effectively estimate harmonics even at high noise levels. In conclusion, SW-LMS provides an effective technique for harmonic estimation.