Abstract: Advanced composite grids structures (AGS) have found many applications in the aerospace structure engineering. A load reconstruction method was investigated to estimate low velocity impact load on an AGS plate by the authors. In the part, an approximate method was presented to calculate transverse low velocity impact responses on an AGS plate. Considering the rib section eccentricity e and stretch blending coupling effect, an AGS plate equivalent stiffness model was improved. Based on the improved model and the unsymmetrical Mindlin plate theory, an AGS forward response approximate model was built with state-space equations. Fourier series expansion was utilized to solve the dynamic equations. The practicability of the presented method in this part was examined by numerical experiments and good results were obtained. The study would provide a theoretical basis for the load reconstruction on AGS plate Ⅱ : Inverse solver.