In Tao’erhe Depression，abnormally high pressure is generally developed and its evolution is inherently connected with hydrocarbon generation，migration and accumulation. The various periods of formation pressure evolution and the episodic hydrocarbon generation，migration and accumulation can be effectively determined by restoring paleo formation pressures and making a comparison among divisions of thermal evolution stages of organic matter. The flow patterns of formation fluids are identified in the different periods of pressure evolution. In Chezhen Sag，there were2processes of overpressure accumulation and release during the formation pressure evolution，with the microfractures formed during the early overpressure accumulation becoming the main pathway for primary hydrocarbon migration. The secondary pores and microfratures formed during the late overpressure accumulation can serve as the pathway for great secondary hydrocarbon migration and the space for hydrocarbon accumulation.