Ozone is an important minor constituent of the natural atmosphere, whose average content is 10^-2-10^-1μg/cm³. It mostly gathers in 10-30km stratosphere, only about 10% is distributed in troposphere. Ozone plays an important role in atmosphere chemistry, and it can protect human and environment in stratosphere. But if ozone content is too high in troposphere, the health of human will be harmed.Ozone in troposphere results from photochemical reaction of NOx or/and hydrocarbon released by natural and artificial sources. Recently, with the increase of autombiles in possession and the use of fuel, oil products and organic dope, the concentration of NOx and VOC rise in atmosphere. Ozone pollution in troposphere is more and more serious. In this article, a network of sampling stations is designed and optimized, ozone and its precursors NO₂, NOx are monitored in Beijing, and the current important characteristics of ozone pollution are analyzed and described. Through analyzing and processing data, ozone formative mechanism in troposphere and correlativity between main precursors concentration and ozone in troposphere are discussed.