Abstract: Gaogou Formation of upper Cretaceous in Xixia basin is a set of alluvial fan and braided stream deposits under the semiarid climate condition,in which 9 sedimentary types and 3 kinds of sedimentary environments have been distinguish- ed,and 6 ichnogenus and 10 ichnospecies have been found in the flood plain deposit and very shallow lacustrine deposit. On the basis of synthetic analysis on sedimentary characteris- tics,the composition and the evolution of sedimentary se- quences in Gaogou Formation are discussed,and the sedi- mentary environment model of the Formation is presented, which accounts for the feature of the palaeoenvironment where dinosaur eggs were formed.