Abstract: The distribution of concealed oil accumulation is controlled by the fore part of delta, nearshore fan and turbidite fan in Gaoyou sag.The availability of subtle traps is related to sand content, and seal condition is better while sand content is 15%~35%. Fault is the key factor of subtle traps to oil accumulation, and has the function of linking reservoir and lateral sealing.There are four types of subtle traps in Gaoyou sag, Which is fault-lithologic trap, sandstone up pinchout trap, lens trap and stratigraphic onlap trap.Different subtle traps are distributed in different areas.Oil exploration practice of LMZ and MJZ oilfield has proved that concealed oil and gas accumulation has large exploration potential in Gaoyou sag, which is the main direction in developed area.