Abstract: Raoyang sag, an important region for oil-gas exploration, is located in the middle of Jizhong depression of Bohaiwan basin. The geologic conditions and patterns of hydrocarbon accumulation were researched by using theories and methods of modern reservoir formation, geophysics, geochemistry, and the data of geology, seismic and analysis assay. The results show that this area is likely to be a large-or medium-sized oil-gas field with abundant oil sources, good reservoirs, developed sets of effective reservoir-cap rock assemblages, multiple types of traps, and good allocation of various reservoir-forming factors. Reservoirs were distributed in the tops,slopes and inside areas of buried hills according to characteristics of discovered reservoirs, reservoir-forming conditions and reservoir types. Based on these researches, this paper put forward the enrichment regularity that reservoirs mainly accumulated in the area of near-source, near the fault zone,in the superimposed artesian flow area of hydrodynamic force,in deep depression, on paleo uplift,at a fault edge,at the tops of buried hills, and in high positions of the inside of buried hills.