Abstract: High resolution seismic profiles and previous research progresses have been used to study the characteristics of the tidal depositional system off the coastal area of southeast Liaodong Peninsula. The results indicate that the tidal sand ridges show asymmetrical-mound and oblique progradational reflection configuration on the seismic profiles, topped by active sand waves, suggesting that they are formed by erosion or by erosion and accumulation and still active. There are four NE-SW distributed tidal sand ridges parallel to each other in the study area, whose orientation is agree with the major and minor axes of the ellipses of M₂ constituent. The tidal sand ridges are 35~75 km long and 3~17 m high, 3~7 km wide distributed in a water depth of 40 to 50 m. The sedimentary characteristics of the tidal sand ridges are influenced by the characters of tide and the change in sea level in the study area. The provenance of the sand ridges is multiple, which includes the eroded matters from the ebb current through the Laotieshan Channel, eroded matters from coastal island and neighborhood, river inputs and detritus from coastal currents.