A bag bottom cushioning structure for an inflated air cushion bag is provided at the bottom of the bag and has air columns rendered into a bent configuration to form an extended curved-surface cushioning space. The bag has a first wall, a second wall, and a bottom wall connecting the bottoms of the first and second walls. The three walls form a receiving space therebetween. The tops of the first and second walls form a bag opening therebetween in communication with the receiving space. The bottom wall is provided at intervals with air columns extending toward the bag opening along the first and second walls respectively. The two inner lateral surfaces of the bottom wall are bonded together by one or more fixedly connecting portions such that the air columns on the bottom wall are bent, and thus protrude, away from the bag opening, forming the extended curved-surface cushioning space.