Abstract: This paper proposes a full state feedback control method based on linear quadratic optimal control（LQR） for a DC power grid electrolysis hydrogen system composed of renewable energy sources. A small signal model with full state error is established, and the system state error feedback method is used to improve the dynamic characteristics of the DC-DC converter, improve the operational efficiency of electrolysis equipment, and prolong the life of materials in the tank under the power supply interference and load fluctuations caused by the integration of new energy sources into the grid. The results show that this method can significantly reduce the voltage and current fluctuation time of the system, and compared with conventional PI control, it has a better suppression effect on system interference. Finally, the theory and method proposed in the article were simulated and verified to demonstrate their correctness and applicability.