<p>The torque ripple in synchronous reluctance motors (SynRMs) diminishes speed output quality, adversely impacting high-speed performance, maximum achievable speed, and control precision. Recent research predominantly focuses on injecting detected harmonic currents but often overlooks the spatial harmonics arising from magnetic circuit nonlinearity (MCN). Considering MCN and coupling magnetic field distortion, a multi-frequency harmonic adaptive detection (MFHAD) method with PI controller combining multiple resonant controller (MRC) is proposed to mitigate the torque ripple in this article. Firstly, the nonlinear magnetic model based on reciprocity analytics is developed. Subsequently, the electromagnetic torque model is reconstructed, taking into account MCN and coupling magnetic field distortion. Then, MFHAD is developed which utilizes a least mean square-based adaptive notch filter to extract specific frequency harmonics. An amplitude and phase detection module using moving average filters is adopted to extract the amplitude and phase of flux harmonics, enabling optimal harmonic analysis to derive currents and mitigate high-amplitude low-frequency interference. Furthermore, an optimal harmonic current calculation method incorporating the Lagrange optimization algorithm is proposed. Additionally, PI controller integrating with MRC is introduced to ensure precise multi-frequency harmonic current tracking without static errors. Finally, the experimental results are validated on a 2.5-kW SynRM drive platform. The comparative experiments demonstrate that the proposed scheme can improve the 6<i>th</i> and 12<i>th</i> torque ripple minimization performance by up to 38.54% and 29.56%, respectively.</p>