Aiming at the problem of load resistance disturbance in DC-DC buck-boost converter, a cooperative controller strategy based on disturbance observer is proposed. The nonlinear disturbance observer technology is used to estimate the uncertain disturbance of the load. The observation value information is introduced into the designed cooperative controller, and a cooperative control algorithm based on the nonlinear disturbance observer is constructed. The robustness and stable track of the expected capacitor output voltage is achieved. Finally, the feasibility and effectiveness of the proposed method are verified through a series of simulations.