Abstract: The chemical properties of clay reflect its depositional environment and the depositional environment affects the engineering properties of clay. Their correlation is an important research content of soil mechanics. The test methods for the chemical properties of soft soil pore solution are introduced, and the tests on upper Shanghai clays are carried out. The distribution of each chemical properties index is given. Combined with the sea-level change in the Shanghai region, the history of changing depositional environment is reflected by the chemical properties of shallow Shanghai clays. Especially the Quaternary transgressive and regressive impact on chemical properties of clay is examined. The correlation between the chemical properties of Shanghai clays and their physical and mechanical properties is analyzed. Two opposite influences of salt content on sensitivity and physical parameters in different depositional environments(transgression and regression) are obtained.