The purpose of the paper is to greatly improve the natural frequency of the embedded co-cured composite damping structure and optimize its stiffness. The embedded co-curing damping composite structure was taken as the research object. The natural vibration characteristics of the structure and the cruciform stiffener structure were compared and analyzed by the finite element method. The influence of the reinforcement width and height on the natural frequency of the structure was obtained. The results show that the reinforced rib could greatly improve the natural frequency and stiffness of the thin plate structure. The natural frequencies of the reinforced thin plate structure get increased with the increase of the rib height, and the first order natural frequency increases the most. Increase of the width of the ribs could increase the natural frequencies of the thin plates. When the width of the rib is large, the increase of the natural frequency could be reduced.