The invention belongs to the technical field of medical instruments, and relates to a device for humidifying and atomizing oxygen, stabilizing pressure and externally medicating when a patient inhales the oxygen. During atomized oxygen inhalation, a flowmeter regulating valve is closed, a smoothbore type humidifying and atomizing conversion valve is pushed to an atomized oxygen inhalation position, the flowmeter regulating valve is opened, and the oxygen directly enters an atomized oxygen inhalation connector and is provided for the patient for atomized oxygen inhalation through an atomization mask connected with the atomized oxygen inhalation connector; after atomized and medicated oxygen inhalation is finished, the flowmeter regulating valve is closed, the smoothbore type humidifying and atomizing conversion valve is pushed to a humidified oxygen inhalation position, and the flowmeter regulating valve is opened to restore common humidified oxygen inhalation. The device is characterized in that the problem of converting humidified oxygen inhalation and atomized oxygen inhalation of a medical institution is solved through the smoothbore type humidifying and atomizing conversion valve on a humidifying bottle, a sterile seal medicating port and an explosion-proof pressure release valve are arranged, and secondary pollution and medical accidents of bottle explosion are more effectively avoided; moreover, the medical cost is not increased, the operational process of medical staff is simplified, and the treatment effect is improved.