【Objective】 The Pearl River Delta Plain, located in South China, has a more-than-one-thousand-year cultivation history, so that the soil therein has been subjected to impacts of intensive anthropogenic activities in its evolution. The knowledge of how the soil evolves under anthropogenic activities is sure helpful to sustainable utilization and management of the soil resources. Being highly active and geochemically sensitive, iron oxides in soil tend to be affected by any slight change in environmental condition in formation and property, so they are often used as an indicator of soil pedogenic process, and considered as a function of soil genesis and development. Therefore, characterization of soil iron oxides has been one of the major fields of the study on soil genesis. In this study an investigation was performed of characteristics of iron oxides in bulk soil and soil clay relative to cultivation age and affecting factors in the Pearl River Delta Plain, in an attempt to reveal how the soil forms and evolves under anthropogenic cultivation in the region. 【Method】 Samples were collected from genetic horizons of the soils derived from marine deposits with cultivation age being 30 a, 100 a, 600 a and 1000 a, separately, of the soils derived from fluvial deposits with cultivation age being 200 a, 400 a, 900 a and 1 000 a separately and of the soils derived from delta deposits with cultivation age being 50 a, 90 a, 150 a and 350 a, separately, in the Pearl River Delta Plain for analysis of physicochemical properties, and total iron (Fe_t), free iron (DCB-extractable iron, Fe_d), ratio of Fe_d to Fe_t (Fe_d / Fe_t) in bulk soil and clay (Fe_d(clay)/Fe_t(clay)), Fe_d sedimentation coefficient (ratio of Fe_d in the genetic horizon beneath the surface horizon to Fe_d in surface horizon) and enrichment rates of Fe_t and Fe_d in clay (Fe_t(clay)/Fe_t and Fe_d(clay)/Fe_d).【Result】 Results show that: (1) Among the soils derived from marine deposits, those, 30 a in cultivation age, were all >1 in Fe_d sedimentation coefficient, regardless of horizon; those, 100 a and 600 a in cultivation age, were > 1 only in some genetic horizons, and those, 1 000 a in cultivation age, were all < 1. In the soils derived from fluvial deposits, the generic horizon where Fe_d sedimentation occurred went deeper with the cultivation age. Among the soils derived from delta deposits, those, 50 a, 90 a, 150 a and 350 a in cultivation age, were found to have genetic horizons as deep as 40cm, 45cm, 80cm and 90cm, respectively. (2) In the soils derivd from marine deposits, the distribution of Fe_d in clay (Fe_d(clay)) in soil profile varied irregularly with cultivation age, while in the soils derived from fluvial and delta deposits the content of Fe_d(clay) in soil layers below 40 cm and 60cm depth, respectively, declined with cultivation age. (3) The contents of Fe_t and Fe_d in clay were higher than their corresponding ones in bulk soil, Among the soils derived from marine deposits, those, 30 a and 100 a in cultivation age were lower than those, 600 a and 1000 a in cultivation age, in Fe_tand Fe_d enrichment rate. In the soils derived from fluvial deposits Fe_t and Fe_d enrichment rates increased with cultivation age in the soil layers below 40cm. And among the soils derived from delta deposits, those, 350 a in cultivation age, were lower than those younger in cultivation age in Fe_t and Fe_d enrichment rate. And (4) Fe_d and Fe_tin bulk soil was extra-significantly and positively related to Fe_d and Fe_t in clay, and so was Fe_t(clay)/Fe_t and Fe_d(clay)/Fe_d to Fe_t(clay) Fe_d(clay) and Fe_d(clay)/Fe_t(clay), and Fe _t(clay)/Fe_ttoFe_d(clay)/Fe_d, however Fe_t(clay)/Fe_t and Fe_d(clay)/Fe_d was extra-significantly and negatively related to Fe_t, Fe_d, Fe_d/ Fe_t and clay content. 【Conclusion】With agricultural cultivation going on, Fe_d in the soils derived from fluvial and delta deposits tends to leach down and deposit in the lower and lower soil layers; Fe_d content tends to decline in the hydroponic redox layer of the soils derived from marine deposits; iron oxides tend to increase in enrichment rate in clay of the soils derived from marine deposits, but decline in clay of the soils derived from fluvial and delta deposits. However, the iron oxides accumulating in clay of the soils were dominated with Fe_d, and clay content in the soils is the major factor affecting iron oxide enrichment rate.