Abstract: The East China Sea Shelf Basin lies in the southeast margin of the Eurasian Plate. It is characterized by the feature of east-west zonation and north-south blocking. The east belt of the depression includes the Fujiang Sag, Diaobei Sag and Xihu Sag. This paper selected 11 balanced cross-sections from the Xihu Sag and 2 from the Diaobei Sag. The extensional and compressive ratios of the Xihu and Diaobei sags in Cenozoic were calculated by using the technique of balanced cross-sections. The results showed that both the Xihu and Diaobei Sags were in a stretched state in T50-T34. However, they were different in other stages, for instance, the Xihu Sag was in a compressed state in T34-T12, while the Diaobei Sag in a compressed state in T34-T30 and in a stretched state in T30-T12. Both of them started subsiding since T12. The Xihu Sag had remained in compress since middle Eocene. The three tectonic movements:Yuquan (T30), Huagang (T20) and Longjing (T12), intensified the compression. Together with the history of basin filling, the Diaobei Sag could be divided into four evolutionary stages since Eocene:early-middle Eocene graben-type rifting, late Eocene and Oligocene depression, early-middle Miocene rifting and subsidence since late Miocene. Similarly, The Xihu Sag has also experienced four stages of evolution since Paleocene:Paleocene and early-middle Eocene rifting, late Eocene and Oligocene depression, early-middle Miocene reversion and subsidence since late Miocene. The Xihu and Diaobei sags are very different in terms of tectonic evolution that is the reason of the north-south zonation in the East China Sea Shelf Basin.