By means of two dimensional structure-stratigraphy interpretation of several seismic profiles, cross-section balancing, and calculation of extension amount and extension rates, the paper investigated developing process of the Binxian-Wangfu sag and analyzed the structural features and forming mechanism of the basin. The results show that Binxian-Wangfu sag was in the initial stage of rifting in the Huoshiling Formation, Shahezi Formation and Yingchengzi Formation, and the fault depression was mainly controlled by normal faults before the deposition of the Denglouku Formation.