The Yixian Formation becomes world well-known by fancy Jehol bita fossils,each signify headway of bita research would bring both here and abroad scientists' attention.As a result of deuteric tectonic destroy and weathering effect,the Jehol bita's palaeogeograpic and basin sedimentary characteristics are hard to make detailed field works and nethermore research.This systematic field sedimentary indicates that 6 sedimentary strata of Yixian formation formed in different phases of passive continental margin to foreland basin evolving process,depositional environment attributes to alluvial fan-braided channel-meander-lacustrine system.From lower Laogonggou stratum up to Jingangshan one,the sedimentary environment was continuously changed.The lithofacies and rock sets was frequently replaced.The sedimentary clast abundantly supply,so the basin was rapidly filled in.The full sedimentary history could be divided into channel and lacustrine types.Fluvial facies possesses main body of early period,each basin tectonic cycle begins in alluvial-channel facies,they are affected by region geologic,geographic and climatic diversities,then develop into freshwater and saltwater lacustrine environments.In Filling moment,basins of predominating fluvial facies consists of alluvial fan sets,flood plain sets and lakeshore plain-delta sets.Lacustrine sediment models make up of logged-depth and brackish water(gypsiferous)types.