The wide-range change of inertia on the motor shaft in permanent magnet synchronous motor (PMSM) elevator door system results in difficulties in PI controller parameters design. This paper presents an improved linear active disturbance rejection control (LADRC) strategy for PMSM to solve this problem. ADRC was designed to observe and compensate the disturbance caused by rotational inertia and changing load, to improve the control performance, and to avoid the real-time parameter calibration process of controller. The parallel linear extended state observers (LESO) were proposed to improve LADRC's tracking precision and anti-disturbance ability under the condition of limited bandwidth value, while maintain the simple parameter tuning characteristic at the same time. Both simulation and engineering verification showed that the proposed improved automatic disturbance rejection control system achieved better control performance and simplified the calibration process of the controller parameters. The system also has wide applicability to different types of door machine systems. The improved control system can reduce application cost and improve its industrial competitiveness.