On the basis of the reconstruction of the denuded thickness of the main unconformities in the M esozoic using several methods，combined with the well and the seismic information。the original thickness of each structural layers were recovered．Based on the analysis，the Mesozoic Jiyang Depression can be divided into four prototypes：a large inland depression in the Early and M iddle Triassic， in an extruding state in the Late Triassic，when NW —trending faults came into being；an inter—mountain basin under the background of weak extrusion in the Early and M iddle Jurassic；and a rift—basin in the Late Jurassic and Early Cretaceous；a sag basin in the I，ate Cretaceous．