Abstract: The study on the characteristics of size of modern sediments demonstr-ates that the sediments of varied types formed in different sedimententation environments possesse the diversified characteristics of size．The character-istics of size in Yarkant Basin's sediments indicate that the first category is similar to the sediments of middle type．The middle type sediments own the characteristics intermediate between water flow sediments and mud-rock flow sediments，whose selection appears bad and content degree of clay and silt is smaller than 10% ．The size analyse may distinguish rather finely the diverse types of sediments，reflecting different sedimentation environm-ents．