In the Quaternary period, the alternating transgression and regression created alternating aquifers and impermeable layers. The coarser sediments play the role of aquifer while the fine sediments play the role of impermeable layers. Groundwater in the beds formed during transgression is usually saline, but groundwater formed during the regression is usually fresh. Besides, during the regression groundwater passes through the freshing with various mechanisms. In vertical direction, there are two main aquifers qh and qp and they play the main role in the water supply in the Red River delta plain. Their water potential and chemical composition have close relationship with stratigraphic and paleogeographic factors.