The DC/DC converter in the DC microgrid is the core device that supports the efficient grid connection of power electronic drive devices such as new energy generation units and energy storage devices. In view of this, this paper proposes a nonlinear optimal control method for DC/DC converters based on differential geometry theory, aiming at the nonlinear characteristics of the mathematical model of the converter. First, the topology structure of the DC microgrid is analyzed, and the mathematical model of the DC/DC converter is established; Secondly, the basic principle of power system nonlinear control based on differential geometry theory is discussed, and the nonlinear optimal controller for DC/DC converter is designed based on the accurate linearization method in differential geometry theory to quickly suppress power disturbance and realize the efficient grid connection application of power electronic drive equipment. Finally, the correctness and effectiveness of the proposed nonlinear optimal method were verified based on MATLAB/simulink.