Abstract: The tectonic division and the analysis of their plane restoration are basic geological issues, and also main tasks during basin survey for regional scrutiny. Based on 2D/3D seismic and drilling data, according to the distribution of faults, the T₀ structural maps of reflection layers, and the ΔT₀ and strata pinch-out line, the Kaiping Sag, Pearl River Mouth Basin could divided into five sub-sags (the west sub-sag, north sub-sag, southwest sub-sag, main sub-sag, and east sub-sag) and five tectonic zones (Nos. 1–5). On this basis, combined with the balance profile analysis, the structural evolution of the Wenchang Formation during depression period of the Kaiping Sag could be divided into six developmental stages in two episodes, during which the sag evolved from the “north dip fault” to the “south dip fault”. The early isolated sags began to expand, and interconnected gradually. The periodic activity of boundary faults controlled the sedimentary development and distribution. The center of structural activity of the sag trended to shift southwestward, and so did the sedimentary center of the main sag body. The main sub-sag and the north sub-sag in the middle of the sag have the largest extension, followed by the southwest sub-sag and the east sub-sag, and the west sub-sag has the smallest extension. The tectonic division of the sag in this study could be verified dynamically by plane restoration and shall be more reasonable; and provides a new scientific basis for the study of dynamic evolution and the distribution of hydrocarbon generation center and sand body in the Kaiping Sag.