Abstract: Aiming at the problem of voltage instability at the output port of Bi-directional DC-DC Converter in DC microgrid, a linear active disturbance rejection control strategy with known disturbance model description and unknown disturbance second-order description coordinated compensation is proposed to reduce the observation burden of linear expansion state observation and improve its observation accuracy, And further improves the anti-interference performance of the auto disturbance rejection control system. Through theoretical analysis of the system performance, the reason why this control strategy can improve voltage disturbance fluctuations is explained. Finally,through simulation and experimental comparison, it is shown that the improved ADR control system is better than the PI control of the outer loop of voltage and the inner loop of current and the traditional ADR control in terms of immunity and robustness.