Based on the advantages and disadvantages of existing active protection system, this paper proposes a new type of airbag active protection system. The components and working process of the system is introduced. Then taking the physical process of airbag active protection system against a rocket projectile as an example, a 3D finite element model (FEM) of airbag and rocket projectile is set up. With the assistance of the software LS-DYNA3D, through performing the simulation when the rocket projectile touched the airbag with an angle 30° from the normal interface, the intercepting efficiency is calculated and analyzed in the simulation. Results show that airbag can deform and rupture the metal jet generated by the rocket projectile, thus greatly reduce its armor penetrating effect. Finally, it shows excellent protective effect of the airbag active protection system.