In order to improve the ability of disturbance rejection and noise suppression of the permanent magnet synchronous motor (PMSM) speed regulation system, three kinds of linear active disturbance rejection control (LADRC) were designed for the PMSM speed loop such as the traditional LADRC (TLADRC), the high-order LADRC (HLADRC) and the reduced-order LADRC (RLADRC). The differences among the proposed LADRC were the linear extended state observer (LESO), such as the traditional LESO (TLESO), the high-order LESO (HLESO) and the reduced-order LESO (RLESO). The stabilities of the speed loop controlled by the three LADRC were demonstrated by employing the superposition principle, and the convergence conditions of the proposed LESO were analyzed at the same time. And then, through frequency domain analysis of the various LESO, it could be concluded that TLESO had the maximum phase lag, which resulted in the worst disturbance estimation ability. HLESO had the maximum amplitude gain in mid-high frequency areas, which made the robustness the worst, while RLESO had the minimum phase lag, which led to the best disturbance estimation ability. Finally, the simulation of the PMSM speed loop controlled by the various LADRC was carried out by using MATLAB/Simulink, and the simulation results verified the conclusion of the frequency domain analysis. The speed curve with TLADRC had the biggest speed dropped in resistance to disturbance, the speed curve with HLADRC had a little oscillation, and the RLADRC had both excellent resistance to disturbance and noise suppressing ability. The obtained conclusion can provide powerful support for selecting LESO in LADRC, and provide a theoretical basis for optimal design of PMSM speed control system.