Bandwidth-based controller tuning method has been maturely applied in the cascaded closed-loop control scheme for the permanent magnet synchronous motor (PMSM). However, when occurs the field-weakening, the non-linearity of the voltage closed-loop hinders its application. Thanks to the nonlinearity precalculation and the introduction of the motor speed, an adaptive field-weakening controller is proposed with explicit tuning criteria according to the bandwidth-based idea, and the bandwidth is the only parameter that needs to be set manually in the tuning process. Through pole placement, the stability of the proposed scheme is strictly guaranteed. Besides, according to the same idea, a q-axis current compensator is proposed to alleviate the voltage overshoot and improve the dynamic performance. The effectiveness is experimentally verified through a 2.2 kW PMSM test bench. The merits of the proposed unified bandwidth-based tuning method for PMSM field-weakening scheme lie in simplicity, good feasibility, and versatility.