To study the application of airbags as a temporary plugging device in the tunnel engineering, the force analysis model was established to obtain the change law of the inner pressure and shape of the airbag as the external pressure increases. Two kinds of failure modes and three control conditions that need to be met during normal operation were obtained, in particular the unique control condition that the external pressure cannot be greater than the internal pressure. Since the matching degree between the airbag diameter and the tunnel directly affect the sealing effect, it is important to determine the allowable error range of the airbag diameter in the engineering design. Then the model tests were carried with three airbags with different matching degree. The deformation, internal and control conditions of the failure limit state were obtained. The results show that the airbag with the smallest deviation has the best sealability and the deformation and failure modes of the airbag are in good agreement with the theoretical formula. The airbag with a larger diameter has wrinkles, but the blocking effect and failure mode are similar to those with a moderate diameter. The smaller diameter of the airbag, due to a part of the internal pressure to offset the tension, has smaller maximum static friction resistance and it tends to slide under the external pressure. The allowable error of the airbag diameter is proposed, providing the basis for airbag manufacturing process.