Lou soil (a well developed agricultural soil) in Loess Plateau can be sorted as a subgroup under the eumorthic anthrosois in the Chinese Soil Taxonomy (Revised Proposal). Soil moisture regime is an important diagnostic characteristic of the anthropic cumulic epipedons (the earth-cumulic surface horizon) and the sub-surface horizon (the argic horizon) of the diagnostic surface horizon. With soil retention capability, evaporation capability and soil water movability as starting point, soil hydrologic effect of the earth-cumulic surface horizon and the argic horizon of Lou soil is discussed in this paper.