Based on the synthetic seismogram calibration and seismic attribute analysis, a series of thick sand bodies developed in the third member of Qingshankou Formation in Haituozi -Dabusu area, southern SongLiao Basin were characterized by banded sedimentary characteristics of long, straight and narrow shape. There are some assumptions for their genesis proposed by many scholars, such as aeolation, tide, fluviation and slump, but none of them could interpret the distribution features accurately. This result showed that Haituozi-Dabusu area is located in slope break belt, with large terrain drop height and intense fluent vertical erosion, which caused erosion to the substratum, then formed the deep and narrow lake rim canyons which control the deposit of the sand bodies and result in the banded sedimentary characteristics. The combining of the sand bodies and faults in updip direction could possibly form fault- lithologic reservoirs.