Abstract: According to the studies on the fourth Member of Lower Cretaceous Quantou Formation tight sandstones in southern Songliao Basin, combined with previous related study achievements, the authors consider that reservoir space types and features, pore-throat size and distribution, pore-throat connectivity and contributions of pore-throats with different sizes on reservoir properties are main contents of reservoir properties characterization. Among them, blue or red epoxy resin-impregnated thin sections, SEM and micro-CT are mainly used for pore space type identification, pore-throat distribution and connectivity characterization qualitatively. Combined with pressure controlled and rate controlled mercury injection, pore-throat size and distribution, pore-throat connectivity and contributions of pore-throats with different sizes on reservoir properties are characterized quantitatively. Studies on genetic mechanism of tight sandstone reservoirs mainly refer to diagenesis evolution and densification mechanism, genetic types of tight sandstone oil reservoirs, oil emplacement and accumulation mechanism etc. Recovering the reservoir evolution process during geological time constrained by diagenesis evolution and clarifying the time and dominated factors of densification combined with contributions of key diagenesis on reservoir properties are the main aspects for densification mechanism studies on tight sandstone reservoirs. Based on the above, genetic types of tight sandstone oil reservoirs can be confirmed by comparing to oil accumulation history and sandstone densification history. As to the reservoirs for oil emplacement occurred later than tight rock formed, pore-throat structures and their matching relationships determine whether the oil can charge into the tight sandstone reservoirs, while wettability changes control how the oil accumulates in the tight sandstone reservoirs.