The Changling Fault Depression, one of the largest composite fault-depression structures in the southern Songliao Basin, exerts critical control on hydrocarbon accumulation through its multi-stage tectonic evolution and differential development of secondary sags. This study integrates 3D seismic data and regional geological surveys to identify structural styles of secondary tectonic units and analyze sag differentiation within the depression. By combining balanced cross-section techniques with 3D Move structural restoration, we systematically reconstructed the 3D tectonic framework, deciphered the spatiotemporal evolution of fault systems, and simulated migration patterns of subsidence centers. Key findings include: (1) The conjugate interaction of NNE-trending basement faults and NW-oriented transfer faults governs sag differentiation, forming distinct structural zones—a western double-fault graben, a central composite half-graben, and an eastern volcanic basement-modified sag. (2) The 3D dynamic model reveals a systematic shift of subsidence centers from Shenzijing to Qianbei and then to Chaganhua, driven by coupling mechanisms between differential fault extension and basement responses. (3) Innovative breakthroughs in 3D structural analysis methodology were achieved, establishing for the first time a technical workflow of "3D dynamic modeling-fault system co-evolution-subsidence migration constraints," which overcame the precision challenges in structural restoration of volcanic basement-modified sags. This research provides essential tectonic constraints for optimizing deep hydrocarbon exploration targets in the Changling Fault Depression, while its 3D structural analysis framework offers a methodological paradigm for studying complex fault-depression basins.