Rapid accurate three-dimensional forward calculation was performed to evaluate gravity anomalies of the top of Cretaceous and various density interfaces above this top.With the "barking method",the gravity effects of the top of Cretaceous and various density interfaces above it were subtracted from the measured gravity anomalies to obtain the residual anomaly,and on such a basis the depth of the bottom of Cretaceous in the study area was calculated through inversion. As rapid three-dimensional inverse algorithm was adopted with a consideration of information on geological and aeromagnetic anomalies, the thickness of Cretaceous was evaluated,and the calculated buried depth of the bottom boundary was more reasonable and precise.These data provide important information for the basic research and appraisal of the oil and gas rosources in Dongting area.