Airbag, due to its deterministic impact load direction, is applied to many interplanetary exploration missions abroad as a landing buffer device. Although the finite element analysis can obtain relatively accurate response prediction results, it is not practical in the early design take into account the high cost of modeling. A simulation analysis method of a horizontal ellipsoidal airbag is studied in this paper. Firstly, the dynamic approximation model of airbag is established from the vibration equation, and the simulation process is developed; the results of approximation model and FE model have been compared by important parameters including a dynamic process of whole airbag to cushion the landing and overload. Finally, the influence of airbag fabric elasticity on buffer characteristics based on the approximate model is studied. The results show that the theoretical approximation model, considering the fabric elasticity, can reflect the landing cushioning characteristics of the horizontal ellipsoidal airbag, and it can better balance the accuracy and efficiency of simulation analysis.