Lake Nasser is one of the largest man-made reservoirs, that is located on the Nile River. To understand the sedimentation process of the lake, bottom sediments from the bottom-surface of the lake core samples from the top 1.25 m of the bottom layer were collected. These samples were mechanically analysed in the laboratory. The analysis of statistical parameters of the sediment samples has generally classified the lake into two depositional environments that reflect the sedimentation process; (1) the riverine environment that exist at the entrance of the lake between El-Daka and CC stations, (2) the lacustrine environment that extend along the rest of the lake to the High Aswan Dam. Along the riverine environment, the river processes were the prevailing, which being reflected on the bottom sediments that are nearly free from clay and composed mainly of sand (>87%) mixed with small ratios of silt (57%). X-ray analysis indicated that montmorillonite, kaolinite and illite are the dominant clay minerals. GIS was used to spatially simulate the bottom sediment distribution at the bottom of the lake.