Abstract: A large number of sediments have appeared in the Talun gas pipeline, which leads to serious obstruction in the pipeline.The sediments, water samples and gas samples on site were characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectrum (XRF), scanning electron microscope (SEM), gas chromatograph (GC) and ion chromatograph (IC). It is determined that the sediments are mainly composed of FeCO₃, Fe₃S₄, FeO(OH) and S. Then, the local climatic conditions and the changes of gathered gas were analyzed comprehensively. It is shown that the sediments are mainly a mixture of the corrosion products of CO₂ and H₂S and the accumulation of precipitated S and dust. And accordingly, the formation causes and mechanisms of the main substances in the sediments were analyzed. It is indicated that the excessive fluctuation of H₂S content and the low dew point of the gathered gas are the main formation causes of the sediments. Based on this, several specific countermeasures were proposed to delay the formation of sediments in pipelines.