Abstract: Abstract：Study of the sedimentary characteristics of a typical outcrop section in the south of the Mesozoic Bohai Gulf area and its surrounding areas and lithofacies and paleogeography in the central part of the study area shows that the Mesozoic Bohai Gulf area consists of a series of downfaulted basins controlled strictly by faults, where there is mainly developed an alluvial fan-river-lake sedimentary system lakeshore-shallow lake, beach-bar and semi-deep lake subfacies occurring inside the lake. The alluvial fan-river sedimentary system evolved upward into a lake sedimentary system and then again gradually evolved into an alluvial fan-river sedimentary system. The compressional amalgamation of the Siberian plate,Yangtze plate and North China plate in the Eurasian tectonic domain played a main controlling role in the Jurassic basin filling in the Bohai Gulf area and the strike-slip motion of the Tanlu fault played a main controlling role in the Cretaceous basin filling in the gulf area.