Abstract: A normal soft landing process using a gas-filled bag can be decomposed into two physical stages: the first is the adiabatical compressure of airbag, then the second is the release of landing shock energy. Based on the thermal dynamic and rigid dynamic equations, the analytical model of soft landing airbag is developed, thus a simple and quick numerical solving method of cushioning response is presented. As an example, the parameters determination method of a vertical cylinder soft landing airbag for an unmanned aircraft is proposed, and these parameters refer to the height of airbag, the bottom area of airbag and the area of vent orifices. The cushioning time history of the soft landing airbag with different types of vent orifices including no gas bleed, with a constant-area orifices and with a controllable orifices, are calculated by a Matlab program. Compraring with these simulation results, the advantages and disadvantages of different soft landing airbags are concluded, and some improvement advice on the design of a soft landing airbags are proposed to help the engineering applications.