The invention discloses a chemical oxygen generating device. The chemical oxygen generating device comprises a box. A reaction cavity is formed inside the box, a liquid level sensor is arranged on the inner all of the reaction cavity, a discharging opening is formed in the bottom of the box, a first electromagnetic valve is arranged on the discharging opening, an oxygen outlet is formed in the top of the box, a second electromagnetic valve is arranged on the oxygen outlet, and an air pressure gauge is arranged on one side of the oxygen outlet. According to the chemical oxygen generating device, hydrogen peroxide is injected through a feeding opening, pistons are pulled through electric stretchable rods, and the hydrogen peroxide is sucked into piston cylinders and stored, and then is put into a reagent pipe filled with manganese dioxide through the feeding opening; when oxygen needs to be generated, the electric stretchable rods push the pistons to inject the hydrogen peroxide into the reaction cavity, and the hydrogen peroxide is reacted with the manganese dioxide in the reagent pipe; meanwhile, the electric stretchable rods are matched with the pistons, the liquid level height of the hydrogen peroxide in the reaction cavity is changed, the contact area between the hydrogen peroxide and manganese dioxide is changed accordingly, and the oxygen generating rate of the whole device is controlled.