The invention discloses an airbag for an automobile. The airbag for the automobile comprises a main airbag and a two-stage gas generator arranged in the main airbag. An axillary airbag is sewn on the outer surface of the main airbag, an air hole is formed in the position, corresponding to the axillary airbag, at the surface of the main airbag, the air hole is sewn with an airtight air duct, one air outlet of the two-stage gas generator is communicated with the main airbag, and the other air outlet of the two-stage gas generator is tightly docked with the air duct. The airbag for the automobile is provided with the main airbag and the axillary airbag which can be inflated independently, the axillary airbag is provided with the special air duct and can be quickly inflated, when a relatively severe collision happens, the axillary airbag can be inflated within a short time and immediately fulfills the buffering function, then the main airbag can be expanded, and thus a more all-sided protection effect can be achieved. Therefore the airbag for the automobile can achieve the more all-sided protection effect and can meet security protection requirements under all kinds of circumstances.