Abstract: The area offshore Liaohe is the strategic hydrocarbon resources replacement area of Liaohe oilfield. A correct understanding of the characteristics and main controlling factors in hydrocarbon accumulation is of great significance to petroleum exploration in this area. Most of the discovered oil and gas reservoirs are around the hydrocarbon-generation depression, and close to the main faults. However, there are big differences in hydrocarbon accumulation between different regions. The western and middle areas are enriched in oil, while the eastern part is enriched in both oil and gas. The main reservoir types in the western part which is a gentle slope are fault-block reservoirs controlled by antithetic normal faults, whereas those in the middle and eastern regions, which are the steep slope belts, are fault-nose and structural-lithological reservoirs. Combined with the conditions of hydrocarbon accumulation, it was summarized that the main controlling factors in hydrocarbon migration and accumulation are active source rock, conduit system and regional cap rocks. The maturity of active source rocks determines the oil and gas distribution; the conduit system determines the modes of hydrocarbon migration and accumulation; the regional cap rock determines the vertical horizons rich in oil and gas.