Abstract: Leshan-Longnusi Paleoswell is the main body of the Caledonian Paleoswell in the Sichuan basin.According to analyses on the structure of the Sinian,the Cambrian and the Middle Ordovician superfaces and the Lower Permian subface,the paleoswell is divided into two parts with compressional structural stress,the simple anticline in the western part and complex structural belt in the eastern part.Based on the principle of geomechanics,it is considered that the tectonic characteristics of the paleoswell are the effect of latitudinal and meridional inertial force subjected when the Earth,s rotational speed decelerated.And sectional asymmetric fold formed is just the tectonic pooling model of the paleoswell.In accordance with the model,the advantageous districts for large and middletyped oil/gas accumulation are indicated.