Abstract: An internal model control-based observer was derived to estimate uncertainties for current loops caused by parameter variations and disturbances in permanent magnet synchronous motor（PMSM）. Specifically, a state-space model for current loops was set up as an internal model under the condition that the coupling term and the back electromotive force were compensated completely, and an augmented model was constructed by introducing the error variable between a real current and the internal model current. Then, a control law for the augmented model was derived by the state feedback control theory. Finally, observer parameters were optimized by the pole placement. Through simulations and experiments, the superior control performance on suppressing current ripple for better speed regulation in PMSM is verified.