Middle-Low thermochronological data, including apatite fission track, (U-Th-Sm)/He and vitrinite reflectance, were used to analyze the erosion thickness occurring at the two main unconformities. Results shows that, the accumulated erosion thickness at the unconformity T1, developed during late Paleogene, is more than 1000m, and in some tectonic inverse area such as Xiejiawan fault-fold belt, erosion thickness might be larger than 2000m. While the accumulated erosion thickness at the other main unconformity T11, which developed during Late Jurassic through Early Cretaceous, is larger than 4000m, most of which was eroded during the Late Jurassic through Early Cretaceous tectonic event, indicating that the eroded thickness during this period is much larger than that of the unconformity T1 happened at the end of Paleogene. During Late Triassic through Jurassic, the studied area developed foreland basin with a wedge Jurassic strata obviously thicker in the eastern region. The Jurassic sediment thickness in the eastern foredeep was larger than 5000m. The pre-Cretaceous formation in the Triassic and Jurassic outcrop area and some local fault-fold belts in Jiangling sag obtained its deepest depth and highest temperature, thus its Ro% during the Jurassic foreland basin, was buried; The original rifted basin developed during Late Cretaceous through Paleogene was much larger than nowadays residual basin, the thickness of the upper Cretaceous-Paleogene was larger than 9000m, in which the Paleogene might be thicker than 7000m, and the Paleogene in Xiejiawan fault-fold belt of Herong sag might be larger than 3300m.