Abstract: The dynamic changes of the Quaternary pore groundwater quality in the Liaohe Delta are obtained from 10 monitoring sites for three years. The result shows that the mineralized degree of the groundwater is generally high, ranging from 1 to 31 g/L. In the western piedmont plain, the water quality is good, with low salinity. While in the area of southern coastal low plain, the groundwater is brined, with salinity between 12 and 31 g/L. The mineralized degree of groundwater in the east and north alluvial plain ranges from 1 to 3 g/L, as brackish water. In respect to the groundwater chemistry type, the HCO₃-Na type is mainly distributed in the western piedmont plain; the Cl-Na type, in the southern low-lying coastal areas; the Cl-NaoCa type, in alluvial plains in the north and east; while the HCO₃·Cl-Na type, in the northeast alluvial plain. The groundwater quality in the sloping piedmont plain is in good status, with rare changes in most areas. In the southern low plain, the contents of Cl^-, SO₄^2- and Na⁺ as well as salinity keep increasing. The distribution of this type of water is spreading to the surrounding areas. The groundwater components and salinities in the northern alluvial plain fluctuate slightly, with little changes and becoming stable.