Abstract: As an important part of power electronic system, virtual synchronous generator（VSG） has been widely used in distributed generation. When it is operated in isolated island mode, the traditional proportional-integral double closed-loop control is difficult to meet the control requirements. Firstly,linear active disturbance rejection control（LADRC） is adopted to make VSG have stronger immunity.Meanwhile, the traditional extended state observer（ESO） is difficult to achieve ideal observation results with the interference of harmonics caused by the access of nonlinear loads. In order to eliminate the influence of sinusoidal signal disturbance on output voltage in isolated island mode, the generalized integral extended state observer（GI-ESO） is applied to LADRC. The error transfer function Bode diagrams of ESO and GI-ESO are compared and analyzed respectively, and the superiority of GI-ESO in solving sinusoidal signal interference is proved by MATLAB/SIMULINK simulation platform.