Abstract: Dali Man site,Dali Man site section has been divided into three large sedimentary facies layers from the top to the bottom by this study,which are:loess paleosol sequence,fluvial deposit and lacustrine sediments And,four terraces have been discovered in this section.The age of T₂,T₃ and T₄ can be dated 0.15 Ma.B.P,0.5～0.4 Ma.B.P and 0.9～0.72 Ma.B.P respectively by the ages of the paleosols covered on them.The cosmparative research of river terraces in the area of the middle reaches of Yellow River indicates the terraces are most likely to form in some stages,such as 0.01 Ma.B.P.,0.15 Ma.B.P.,0.6～0.5 Ma.B.P.,1.2 Ma.B.P.,1.5 Ma.B.P..The age of T₁ can be dated 0.01 Ma.B.P.by terrace comparison.According to loess sequence covered on terraces,the authors put forward a new model on the forming of terraces in the area of middle reaches of Yellow River:The uplifting of Tibet Plateau enhances the global cool down,both the uplifting of Tibet Plateau and global cool down had positive feedback on the reducing of the base level of erosion.