Based on initial potential data of nearly 4000 production wells and static geologic material including the structure, logging interpretation, sedimentary microfacies and types of abandoned wells, oil—water distribution regularity in the Putaohua oil layer in the Sanzhao Sag, Songliao Basin, was systematically analyzed. Single local (structure, lithologic) trap controls final hydrocarbon accumulations and distribution of oil—water in the tertiary structure. Distribution regularity of oil—water is unifying in the single local (structure, lithologic) trap. Distribution regularity of oil—water is different in adjacent and different single local (structure, lithologic) traps. Layers of oil—water distribution are controlled by distribution characteristics of reservoir, and boundaries of oil—water distribution are controlled by the array modes of fault and sandbody. In similar conditions, oilcontrol capacities are weakened from horst faultblock reservoirs antithetic normal fault structural nose reservoirs herringbone antithetic normal fault reservoirs fault—microstructure reservoirs fault—lithologic reservoirs, lithologic reservoirs other reservoirs.