Abstract: Ozone has intensive absorption in the UV band. By taking in the condition of direct sun, moon, and twilight zenith sky, the UV absorption spectrum is measured with a self–made Solar and Skylight Spectrophotometer. The vertical and slant column amount of ozone is computed by using the method of band absorption. The procedure of measuring and calculating ozone amount is introduced in the paper. Also the preliminary result of ozone under the clear weather condition in Beijing is given here