Abstract: The changes n erosion-deposition pattems of downnstream riaerbed surface after the impoundnent of Three Gorges Project (TGP) are quantified by the river bed surface fractal dimension (BSD).The changing character and the physical mechanism associated with the changes are also analyzed.The study reveals a whole partre lationship between the BSD and each cross-section.The complexity of river bed surface can be well represented by BSD.After the TGP impoundment, there is a significant increase in BSD along the Huyatan and Yidu reaches While, less increase is found for the Guanzhou reach and the opposite result is obtained in the Lujiahe reach.The change in BSD of each river reach is able to characterize the deformation in the river bed surface, which is resulted from the new regime of integrated frictions after the TGP impoundment.The BSD can thus be predicted through analyzing the trend change in each reach, which provides necessary data for studying the new relationship of bed friction and water level.