Abstract: The lithology of sub lacustrine fan is mainly composed of medium-grained to coarse-grained sandstones of middle sorting and pore development. Sub lacustrine fan facies can be divided into three sub-facies: inner fan, middle fan and outer fan. Inner fan and middle fan is mainly high-quality reservoirs, composed by one main channel and braided channel, mainly manifested as minimal zigzag and zigzag bell-shaped curves of gamma logging curve in the logging facies, gully-shaped and imbricate arrangement in the seismic section. Sub lacustrine fan formation in the area was mainly controlled by multivariate as the provenance and the trigger mechanism. Large scale braided river deltas front sand bodies that were from ancient Liaohe river system were a basic geological condition for the formation of sub lacustrine fan. Due to the strong normal faulting, the gradient of slope and the action of waves disturbance, original sediments slumped along with slope, and deposited in the semi deep-deep lacustrine facies. Sub lacustrine fan in the north of Liaoxi low uplift has a certain petroleum exploration potential based on the nearby hydrocarbonrich source rocks, having good reservoir rock, good caprock association, and good migration.