Based on drillings and stratigraphic sections, writers draw maps about uniformly thick residual formation in the Longmen foreland basin since the Late Triassic Epoch with Surfer 8.0 software, and figure out the sediment flux in each phase: 300.2g/(m2?ka)， 66.5 g/(m2?ka)， 71.7 g/(m2?ka)， 38.5 g/(m2?ka)， 113.0 g/(m2?ka)， 1204.6 g/(m2?ka). We carry the sediment back to the provenance with the material balance method, and then figure out the speeds of denudation in each phase are: 167.3 mm/ka， 22.5 mm/ka， 22.9 mm/ka， 9.8 mm/ka， 22.9 mm/ka， 319.4 mm/ka. The results show that the speeds of denudation and the sediment flux increased initially and decreased aferwards. The erosion—deposition process was the strongest in the Late Triassic Epoch and the Late Cenozoic, which may be the two period with strong uplifting in the Longmen Mountain area. Based on estimating the total volume of sediment, with the principle of material balance, we could draw the conclusion that, since Longmen Mountains began to uplifte in Late Triassic Epoch, the Longmen thrust belt uplifted above 10~12 km, and the aggregate thickness denuded is more than 7.05 km.