Abstract: Xihu sag is a Cretaceous-Tertiary basin which experienced multi-episodic tectonism. Complicated tectonic styles and geological structures were generated by multi-episodic rifting and inversion. Zonation in latitudinal direction and blocking in longitudinal direction is the main feature of the Xihu sag. Faults developed in synrift phases formed several structural styles: the fault terraces, grabens and horsts were generated in the western slope belt; fracture assemblages in the central depression belt were the complex Y-type fractures, feather fractures and flower-like fractures; while in the eastern fault terrace belt the Y-type fractures, comb-like fractures and feather fractures were generated during the phase of inverted tectonism. The synrift faults developed in early phase formed several structural styles, such as backwash imbricated structures and posthumous imbricated thrusting structures. Combined with tectonic styles analysis, the control effects of evolution of the basin and the process of sediment filling to trap development are discussed, which is an important guide to the petroleum prediction of hydrocarbon enriched sag.