A new type of large semi-rigid solar array structure with a new structural concept of rigid-flexible combination has developed for space application. Due to the good features of large scale and lightweight, such structure can well satisfy to the large power requirements of spacecraft and thus has drawn increasing attention recently. However, its structural weakness of inherently flexibility makes low frequency vibrations happen much easier. It is highly required to obtain an accurate dynamic model for predicting the dynamic characteristics of this kind of semi-rigid space structure. Because this structure is composed of different components that have quite different stiffness properties respectively, it is very difficult to build up an accurate dynamic model of this complex structure. In this paper, a novel analytical dynamic model is developed for solving this problem. To validate the correctness of the proposed model, experiment studies are conducted. By comparing the simulation results with experimental results, it can be concluded that this dynamic modeling method presented in the paper is credible. The present study is significant for the structural construction and application of this special structure.