Abstract: The oil-water differential accumulation in the Chang-8 member in Huaqing area of the Ordos basin is the primary problem that has constrained the further development and deployment of the oilfield for a long time. The sand bodies in the underwater distributary channel are the dominant oil reservoirs in Huaqing area, and the fine description for the underwater distributary channel is conducive to solving the complex problems on oil and water accumulation. Based on the concepts and knowledge of channel architecture, the paper selected the typical rock samples of river main body and flanks of the Chang-8 member in Huaqing area, and performed microscopic identification and statistic analysis on lithology and microcapillary mercury injection data. The results reveals the physical properties and pore structures of the main channel sand bodies are far better than those of channel flanks; under the same conditions the main channel sand bodies are more favorable for crude oil charging, channel flanks make reservoir’s heterogeneity strengthened, which influences the differential distribution of oil and water. Based on the establishment of sand body profile and reservoir model, the composite channel sand bodies can be classified into 4 types. The thickness of the main channel sand body is an important index to determine the scale of a reservoir, and the size of the sand body determines the migration and accumulation of crude oil. Limited crude oil migrated along the large-scale channel sand bodies and accumulated at pinchouts or the higher positions of structures