On the basis of fine seismic interpretation

various methods including fault throw method

fault activity intensity method

balanced cross-section technique and physical simulation are adopted in this paper to analyze the Cenozoic tectonic characteristics and evolution process as well as the forming mechanism of structures. The results show that the northcentral part of Jizhong Depression was dominated by extensional structures in the Cenozoic

with strike-slip structure style also occurring. In Baxian Sag

tilting and sliding fault terrace structural styles were predominant. While Raoyang Sag was dominated by anticline structural style except for its northernmost part where strike-slip structure style was common. The extensional intensity shows large diversity in different periods in both Baxian Sag and Raoyang Sag

strictly controlled by the activity of boundary faults. Raoyang Sag was controlled by Liulu

Hejian

and Maxi faults from south to north. The extension of sag as characterized by transition from "south being larger than central-north"in Ek- Es4to "central-north being larger than south"in Es3- Ed. Baxian Sag was controlled by the diversity of Niudong fault activity along strike

featuring in the tectonic evolution of"strong early stage but weak middle and late stages"in south

"weak early stage strong middle stage and weak late stage"in the central

and "weak early stage but strong middle and late stages"in north. The physics simulation experiment validates the fault development process of research area. The experiment result has strong similarity with the development characteristics of the faults

demonstrating the correctness of tectonic geometry and kinematics characteristic analysis. On the basis of above research

the tectonic evolution process of Raoyang Sag and Baxian Sag is divided into three stages

namely weak early stage

strong middle stage

and fair late stage. Finally

the mechanism and deep background of tectonic formation and evolution are discussed.