A vehicle airbag system may include an inflator supplying a gas to an airbag cushion, an airbag housing coupled with the inflator and having a housing vent hole to discharge a part of the gas supplied from the inflator, a retainer mounted in the airbag housing and coupled to the inflator, wherein the airbag cushion covers an opening of the retainer to supply the gas in the airbag cushion, the retainer including a guide hole and a retainer vent hole, and a tether connected to the airbag cushion at a first end portion thereof and fixed to the airbag housing at a second end portion thereof by passing through the guide hole of the retainer, wherein the tether includes a communication portion at the second portion thereof to form a hole therein so as to selectively permit an gas commutation between the airbag cushion and the outside through the retainer vent hole, the housing vent hole, and the hole of the communication portion.