Hailar Basin is Mesozoic-Cenozoic polycyclic and fault-depression composite continental rifled basin. Through the analyses of the structures, sedimentations, hydrocarbon accumulating characteristics and sedimentary environments for Wunan Sub-sag in the basin, the hydrocarbon in the fault basin is mainly generated around the mature source rock area and self-enclosed accumulating system with short-distance migration. The rest resources are enriched in the tight sandstone-siltstone interbeds of water-transgression and high-stand system tracts of the hydro- carbon-generating sag, these areas are the the favorable plays of the unconventional oil and gas, so the further ex- ploration of the unconventional oil and gas reservoirs should be focused on these regions.