This paper analyses the stratigraphic sequence of the Late Quaternary and formation and evolution of the incised valley in the Hangzhou Bay area, on the basis of the geological setting. During the last glaciation, the ancient river incised lowstand old strata, forming a large incised valley with depths of 40-110 m. At the bottom of the valley, there is an unconformity, which is non-isochronous in the landward direction and along the coastline, indicating a typical type-I sequence boundary. The postglacial sequence is a complete type-I sequence but includes many di-astems. The first flooding surface is also non-isochronous, which appears as a boundary between the lag deposits and the retrogressive aggradation in the incised valley and as the top of the pale-osol at the interfluves. The middle of the shallow marine muddy layer dated at 7000-6500 a B. P. , represents the maximum flooding surface, which is the only isochronous surface in the depo-sitional sequence. The fluvial flood-plain sediments of the transgressive system tracts is the main exploratory target of industrial biogas.