Abstract: First of all, this paper relates N.S.Schatski's researches on aulacogen and the development of its conception with the advent of plate tectonic. It is suggested the Early Paleozoic sedimentary basin of the west part of Zhejiang Province is an aulacogen with NEE extension and the Caledo-nian geosynclinal-folded zone of South China located at the south side might take a turn from north east-east to north in the area out of the mouth of Yangtze River. The aulacogen was confined by two boundary faults and opened eastward as horn shape.Its range showing in the spread of sedimentary geological body is completely coincided with the convex of the Moho's surface. The upward amplitude of Moho's surface progressively increases eastward, which indicated the amplitude of basin subsidence to be inhanced along the same direction. It also accords with the geological facts. The evolution of the aulacogen underwent three stages: the hot uplifting and graden type rifting, the broad downwarp and the rapid filling and dying out. Seven formations were deposited accordingly in continental and shallow sea environments. This evolution feature is similar to that of typical aulacogen and has a close relation with the evolution of Caledonian geosynclinal-folded zone of South China. Both of them were synchronous in development and had a similar evolutional direction and stages. On the other hand, their properties of formations are markedly different from each other. These show that they were formed by same deep geological process but underwent different developments and environments afterward.