Abstract: In order to study the structural features of Yingen-Ejinaqi basin and provide foundations for further oil and gas resources investigation and evaluation, the characteristics and causes of gravity field have been discussed and analyzed, and the fault systems have been speculated through collecting, processing and studying the existing gravity survey data in the area. Regional gravity anomalies in study area are mainly aroused by the undulation of Moho surface. On the one hand, gravity high and gravity low of residual gravity anomaly with alternative distribution reflect the distribution range and through-going features of the sag and uplift; on the other hand, maybe reflect the asymmetric faults which develop between the sag and the uplift in study area. Two mainly groups of fault, which play an important control role in the structure and properties of the basement, framework of uplift and depression and distribution of Mesozoic basin, with NEE (NE) and NWW trend respectively developed in the study area. The basement faults divide the study area into multiple blocks, which made the Basin with the features of alternate sag and uplift.