Sia paddy soils derived from three different parent materials were sampled from the Chengdu Plain which was one of the most important rice-growing regions in China to study the characteristics of the differentiation of iron oxides in various forms and its relation to the formation of the specific genetic horizon. Tlte results showed that the extent of the variation of iron oxides in various forms in the paddy profiles studied decreased in the following order: amor. iron oxide > free iron oxide > total iron. It was revealed that the content of total iron was closely related to the parent material from which the paddy soil was derived, and the content of free iron was positively linearly related to the content of total iron in the paddy soil, which suggested that it was also related to the parent materials to some extent, but the content of amor iron oxide was greatly influenced by the environmental conditions.