In fluvial-delta depositional environment，the main reservoir is thin bed channel sandstone which is very important in China′s onshore lithological reservoirs. In this study，the channel geomorphology of the 5th interval of Xujiahe Formation （T3x5）has been mapped using seismic sedimentology. The result shows that channel geomorphology of T3x5 is similar with modern channel belts in channel-flood plains. By seismic geomorphology technology，channel belts，main channels，distributary channels and abandoned channels can be distinguished in striatal slices. Main channels which have very clear morphology are characterized by width <1.1 km and length on the order of tens of kilometers. Distributary channels or abandoned channels with blurred morphology are characterized by width <100.0 m and length <5.0 km. Main channels are relatively immobile，so they are easy to preserve after deposition. In contrast，distributary channels which are apt to cause avulsions are vulnerable to rework by erosion. In channel belts，superimposed channel bars are favorable lithological reservoirs，which is characterized by width up to 5 km and thickness up to 37 m. This study shows that seismic sedimentology is a useful approach to map thin bed sandstone in the lithological reservoirs.
