Abstract: The paper studied detaily the sedimentary facies of the 3rd member of Hetaoyuan formation(H_3) in Biyang depression, using the petrographic signs,and signs of elextro - facies; It also revealed the sedimentary facies' types(fan- delta, braided river delta,lacustrine facies and their micro- facies) of the H_3 in Biyang depression;there are large areas of reservoirs which developed in the upper of the H_3;the H_3 in Biyang depression is perennial salt lake deposits alternating with dilute phase and salinization period,generally,the salt lake experienced the evolution of process which was from deep to shallow then to deep again and the same with light to salt then to light.