Abstract: A passive controller based on Euler Lagrangian (EL) model is designed to solve the problem of large voltage fluctuation and even instability in optical storage microgrid under the condition of light intensity change and load disturbance. Firstly, the system structure of optical storage microgrid is given, and two working states of bidirectional DC-DC converter are analyzed. Then, by establishing the EL model of optical storage microgrid control system, the system is described from the point of view of energy, and the passive controller of bidirectional DC-DC converter is designed by injection damping method. When the lighting condition is good, the photovoltaic cell can not only meet the power supply demand of the load, but also store the remaining energy into the battery through the bidirectional DC-DC converter. When the lighting condition is weak, the electric energy in the battery can be provided to the load reverse through the bidirectional DC-DC converter to ensure the normal power supply of the load, and the system can run stably and efficiently when the light intensity and load change. Finally, the feasibility and correctness of the control strategy proposed are verified by the simulation of the optical storage microgrid system model built by Matlab/Simulink.