Abstract: According to seismic phase analysis,the corresponding sedimentary characteristics were studied.The medium-strong amplitude of continuous seismic phase indicates braided deltaic plain deposition,medium amplitude of interrupted seismic phase suggests depositional facies of braided deltaic front,and weak or gap seismic phase means mudstones deposited in shallow lake(or interdistributary bay).On basis of above relationship between seismic phase and depositional facies,distribution of sedimentary facies of the Triassic in Tahe area was discriminated,in accordance with its structural setting the potential lithological traps were indicated.