A pressure regulating oxygen bottle has a bottle body filled with liquid, a cap mounted on the bottle body, an outer tube mounted in the bottle body, and an inner tube mounted through the cap and protruding in the outer tube. The outer tube has multiple flow holes arranged linearly between two opposite ends of the outer tube. The inner tube is connected to an artificial respiration system and has multiple communicating holes arranged spirally between two opposite ends of the inner tube. By turning the inner tube to allow one of the communicating holes to align with a corresponding one of the flow holes of the outer tube, a hydrostatic pressure formed between a liquid surface of the liquid and the communicating hole is changed. Accordingly, gas pressure inside the artificial respiration system can be adjusted.
