Corrosion law and mechanism of 20# low-carbon steel in near-neutral soil along Yangtze River in Nanjing are studied by experiments of buried specimens in laboratory. In three kinds of soils, the corrosion features and products are analyzed by EDS and XRD, and the relation of corrosion rates, open-circuit potential and polarization curve with times are tested. The results indicated that corrosion rates changed incessantly along. On the condition of the same times, specimens and different soil samples, the corrosive degree of 1# and 2# specimens are serious, but 3# specimen is serious lightly. The corrosion products are main non-crystalloid, Fe (OH) 3 and Fe2O3.The changing tendency of different times and soils is different, and accordant with that of corrosion rates. The corrosion mechanism is discussed lastly, in near-neutral soils, oxygen is deoxidized and OH- ions are created in cathode area, iron is oxidized and the hydration of Fe2+ ions is created with water from soil in anode area, and Fe2+ are converted into more steady products Fe（OH）3 and Fe2O3.