Abstract: This paper discussed the characteristics of palaeoclimate variation, paleotopography evolution, paleodeposit boundary change, rise and fall and deposition of lacustrine deposit datum level,,migration of subsiding center and sedimentary system evolution in Yanqi Mesozoic prototype basin. Since the lacustrine deposit datum level occurred twice rising in Middle-Late Triassic and late of Early Jurassic, three sedimentary cycles, i.e. Middle-I ate Triassic, early of Early-Middle Jurassic and late of Middle Jurassic-early of Late Jurassic, were formed in the basin. During Triassic to early of Middle Jurassic, a sedimentary system composed of alluvial apron or stream (humid fan)-braided stream-meandering stream-shallow shore lake appeared from margin to center of basin; while in the mid epoch of Middle Jurassic stream sedimentary system occurred.

Key words: Yanqi basin, Mesozoic, prototype, sedimentatary basin, evolution