Abstract: Sub-synchronous oscillation（SSO） in a grid-connected doubly fed induction generator（DFIG） threatens the stable operation of the system. Traditional control strategies may not be effective when the operating conditions of a system change. To solve this problem, a sub-synchronous suppression strategy based on linear active disturbance rejection control（ADRC） is proposed. On the basis of the traditional dual loop proportional-integral（PI） control on the rotor side, an improved auto disturbance rejection control is used to replace the PI part of the original inner loop, in which a linear extended state observer is used to estimate the part of compensation sub-synchronous control interaction（SSCI） in real time. The proposed method involves simple parameter tuning and is strongly robust. By building a DFIG grid connection model and comparing it with PI control, it is verified that the control strategy has good control performance in both steady-state and transient states. By comparing with additional damping control and nonlinear ADRC, it is concluded that improved active disturbance rejection control can suppress sub-synchronous oscillations under multiple operating conditions, converging the distorted current more effectively compared to the simple tuning of existing control parameters, thereby stabilizing the output power of the doubly fed fan system. Finally, the effectiveness of the proposed method is verified using an RT-LAB experimental platform.