[Objective] To address the issue of low position estimation accuracy in sensorless permanent magnet synchronous motor control systems under complex signal interference environments, this paper proposes an adaptive-bandwidth linear active disturbance rejection control (AB-LADRC) strategy. [Methods] Firstly, a multi-source disturbance error model incorporating current sampling noise, quantization errors, and zero-drift was established to explicitly quantify system uncertainties. Secondly, a phase-locked loop closed-loop architecture based on a third-order linear extended state observer was constructed to dynamically observe and actively compensate for the aggregated disturbances. Furthermore, a bandwidth separation filtering strategy was introduced to suppress high-frequency noise amplification. Additionally, an adaptive bandwidth adjustment mechanism was designed to enable the dynamic optimization of observation parameters based on real-time operating states. [Results] The experimental results indicated that, compared with the conventional phase-locked loop strategy, the proposed AB-LADRC strategy limited the speed dip to only 7 r/min during load transient and shortened the recovery time to within 40 ms. Furthermore, under strong noise conditions, the root mean square error of speed estimation decreased by 69.5%. With 12-bit low-resolution sampling, the speed ripple was strictly limited to within ±1.59 r/min. Meanwhile, the amplitude of subharmonic low-frequency pulsation caused by zero-point drift attenuated by 78%. [Conclusion] By decoupling the control dynamics from external noise, the strategy significantly enhances the system’s noise-rejection robustness and high-precision servo performance under harsh operating conditions.