Through a wide-spread groundwater sampling mainly at nested monitoring wells in the Beijing Plain, this study analyzed the water level, hydrochemistry, temperature, deuterium, oxygen-18, 14 C and other aspects. The result indicates that there exits an obvious stratification phenomenon of the groundwater in the alluvial plain area down in the middle part of alluvial -pluvial fans, and the hydraulic connection between layers is very weak. Based on the analysis of the 15 paleowater samples through the deuterium-oxygen-18 method and 14 C isotopic dating, the deep groundwater circulation in the fine sediments area of Beijing Plain down in the fringe part of alluvial-pluvial fans is relatively slow and partly stagnant. The average depth of the paleowater points is about 250m. The main reasons for the formation of stratification and paleowater points are the water-blocking effect of the clay type strata and the compaction effect during the sedimentary process, especially the differential compaction, which could form closed or relatively closed stagnant aquifers. The deep aquifer could not get recharge timely because of the slow circulation and partly stagnant, which contributes significantly to the land subsidence of the Beijing Plain area.