Abstract: The Baiyun Sag,as one of the important hydrocarbon accumulation zones in the Pearl River Mouth basin,is a secondary depression.The formation and evolution of the sag could be divided into three phases:the rifting phase,the depressive phase and the differentiated uplifting-subsiding phase.The structure of the Baiyun Sag is very complicated because of the stacking of multiple tectonic movements.Based upon the basin tectonic evolutionary history,combined with seismic profiles and well logs,we discussed in this paper the tectonic control over the hydrocarbon generation,migration and accumulation in the sag.Data suggest that the tectonic activities since the Cenozoic have rendered strong influence on the formation of the final structural framework of the sag,and played an important role in the accumulation and distribution of oil and gas.