The improvement of the space-to-earth observation range and observation accuracy has created demand for large-scale planar deployable antenna mechanisms. A new space large-scale two-dimensional multi-folding and unfolding planar antenna mechanism， which has been optimized for configuration， structure design， and dynamic characteristics analysis， is proposed in this study. First， a comprehensive evaluation index is established， and the overall configuration of the antenna with the best comprehensive performance is selected. Second， the structure of each part of the antenna mechanism is designed in detail and the prototype is developed. Additionally， the experimental verification of the deployment principle is carried out. Finally， the finite element model of the antenna mechanism is established， and the first five vibration frequencies of the antenna mechanism in the unfolded state and the corresponding mode shapes are obtained through simulation. Further， the cross-section parameters of each member are optimized with the system specific frequency as the optimization target. The folding ratio of the two-dimensional multi-folding and unfolding planar antenna mechanism designed in this study is greater than 17.6， which is an improvement over the folding ratio of the traditional planar antenna mechanism. The vibration fundamental frequency is 1.333 9 Hz， which helps in realizing the high rigidity support of the large planar antenna mechanism and provides a feasible scheme for the development of large planar phased array antenna mechanism in China.