Abstract: To reveal the intensity and timing of inverted structures in Baiyun sag in Pearl River Mouth basin, the quantitative analysis method for inverted structure, including growth index, displacement-distance curve and reversal rate, is applied to quantitative analysis of Baiyun sag抯 inverted structures. The results show that the tectonic inversion happed twice in Baiyun sag. The early inversion began in the Early Oligocene (34.0?06~32.0?06a), mainly developed in the Late Oligocene (32.0?06~23.8?06a), with strong inversion degree; the late inversion began in early Middle Miocene (15.5?06~13.8?06a), mainly developed in late Middle Miocene (13.8?06~12.5?06a), with mild inversion degree. The early inverted tectonic stress contains the gravitational potential created by the intensive subsiding of Baiyun sag and the sinistral compressive?torsional stress produced by South China Sea spreading, of which the gravitational potential is the main controlling factor. The late tectonic stress is mainly affected by the Dongsha movement, so the inversion stress may come from the eastern part of Pearl River Mouth basin, possibly related with squeezed effect of Philippine plate. The late inverted structural trap could be the more favorable area for hydrocarbon accumulation