The article study the genetic classification of sedimentation and physical behavior analysis of the Chang 6-8 reservoir of Triassic Yanchang formation in Longdong area, Shanganning basin by sedimentological method. Intergranular pores and residual intergranular pores are the most important and effect pores, it also include a little of fracture pores. The reservoir stratum include sheet sand over mouth bar, underwater distributary channel,debouch bar,and slip sandstone. It is consider that the sheet sand over mouth bar is the first-rate reservoir, the second is debouch bar, and the rest is not good reservoir. Approach the subject of sedimentation control physical behavior of reservoir from different angles, and consider of that the reservoir of physical compose, constitute and structural features is controlled by sedimentation environment. The reservoir of physical compose,constitute and structural features will control the quality of the reservoir.