Abstract: A suit of huge-thick dolomite formation was formed in the second and up-third of Hetao yuan Formation in Anpeng district of the center of lake-basin of Biyang depression.The main rocks are argillaceo us dolomite,dolomitic mudstone,mudstone,dolomite and trona formation.It is a perennial alkal escence saline sedimentary system.Based on the sedimentary charact eristics of lake-dolomite formation,the author first analyses the sequence of length-cycles,met aphase-cycles and short-cycles from the south to north section,and then the short-cycle and rhythm-cycle by high-resolution sequence stratigraphy method from the aspect of sediment and diagenesis.