Abstract: The accumulation of black powder in transportation pipeline would induce a series of problems, such as blockage of the instrument and valves, pollution of the conveying gas and loss of pipe transporting volume. Therefore, it is necessary to study the composition and distribution of black powder in transportation pipeline. Based on the operation of pigging, the composition, distribution and form of the black powder at different locations in natural gas transportation pipelines were investigated. Correspondently, gas quality of the pipelines in recent years were analyzed as well, leading to the understanding on the composition, distribution, and the possible causes of the black powder in the pipelines. The results showed that black powder prefers to accumulate at the low-lying places closing to gas source. The black power is mainly composed of FeCO₃, and mounts of Fe₃S₄, S, SiO₂ and Fe₂O₃. Among which, FeCO₃, Fe₃S₄, and FeS were mainly formed by CO₂ and H₂S corrosion of pipeline steel, while S, SiO₂, Fe₂O₃ were carried by the upstream gas flow or from the construction residues. The prevention and control measures of black powder were proposed according to the composition and distribution features of black powder in transportation pipeline, including preventing the corrosion of equipment and pipes from the source, cleaning the old natural gas pipeline regularly, and selecting suitable procedures for pigging operation.