The instrument adopts ultraviolet absorption method. The basic working principle is: ozone can absorb ultraviolet light with a certain wavelength (254nm), and the intensity of ultraviolet absorption is related to its concentration. The detection method was as follows: ultraviolet light with wavelength of 254 nm was irradiated in the reaction chamber. Using photoelectric detector, the light intensity of sample gas (ozone containing atmosphere) and reference gas (atmosphere after removing ozone) passing through the reaction chamber are measured respectively, and the light intensity ratio of them is calculated. The concentration of O 3 in the sample gas is obtained by Lambert Beer law.