Urban sewage pipes are filled with flammable, explosive, toxic and other noxious gases, which have brought hidden troubles during system maintenance and operation. To ease these threats to the urban sewage pipeline network, we should perform spot inspection and take some measures against safety risks that may occur on them. But of those, the test of noxious gases is the most challenging. Based on the odor classification method, we take an urban sewage pipe network in Chongqing as a study case for sample collection and spot inspection. The purpose of this paper is to classify and test the methane CH4 and hydrogen sulfide H2S by different methods. Data available from individual supervision spots are compared and analyzed in parallel, in order to explore how to measure these noxious gases and what’s the distribution and concentration change laws of them in urban sewage pipes, hoping to provide the clues to the early warning and safety operation of urban sewage pipeline network.