Abstract: Huaqing area locates at the development area of Chang 7 source rocks, where oil supplies are sufficient and reservoir formation conditions are favorable. Many petroliferous zones have been found; however, the distribution of oil in the area is unbalanced. In some local regions with high porosity and permeability, a large amount of water has been found in well testing, for example, in well Bai 241, etc. Based in the data of well drilling, logging, testing and reservoir fluorescence, it is analyzed in this paper the causes for the complex oil and water distribution in parts of Chang 8 reservoir, Huaqing area, the Ordos Basin. It is pointed out that mudstone layers between the Chang 7 source rocks and the Chang 8 reservoir block the migration of oil generated from the Chang 7 source rocks into the Chang 8 reservoir. The carrier bed between source rocks and reservoir controls the potentials of Chang 8 reservoir. These conclusions provide geological basis for further exploration and evaluation in the study area.