Cylindrical airbag was studied and a theoretical model was proposed, which redefined the relationships among the dynamic stiffness, initial internal pressure and dynamic compression deformation. Dynamic compression test was carried out to get dynamic stiffness characteristics, through which comparison was made between the models and experimental values of different specifications and initial internal pressures. Experiment results showed that theoretical predicted value of dynamic stiffness is bigger than the tested data; dynamic stiffness increases along with the increase of initial internal pressure. Results from calculation and experiments are in good agreement when the initial internal pressure decreases.