The Qiangtang basin is a huge sedimentary basin which is superposed over the Proterozoic basement and developed from the Meso-Cenozoic. The basement of the basin consists of Proterozoic metamorphic rock series, which have the feature of a two-layer structure. The lower part of the basement is the crystallized "hard basement" , while the upper part is the metamorphic "soft basement". The structure of the basement is characterized by two depressions with an uplift in-between. Within the depressions and uplift are a number of secondary fault convexes and concaves. There have developed in the basin two groups of conjugate basement faults trending ENE and WNW respectively, which cut the basement into rhombohedron blocks. The cover structures are obviously controlled by the basement structures.