Abstract: Based on test materials, including of silt, shallow salt groundwater and atmospheric precipitation which were got in northwestern Shandong geochemistry action in the process of freshwater displacing saltwater were studied. The results indicated that (1) When content of clay was high in aquifer medium, and specific conductivity of exudate was less than or equal to 0.83 ms/cm in the process of freshwater displacing saltwater, clay played a role of film effect in concentrating ion components. (2) Dolomite still kept precipitation with water, and halite still kept dissolution in the process of freshwater displacing saltwater. Calite precipitated when specific conductivity of exudate was more than 1.00 ms/cm; Gypsum balanced with water when specific conductivity of exudate was more than or equal to 6.22 ms/cm. Mg/CaNa exchange interaction was remarkable with critical ion strength being in 0.20～0.25 mol/L. Adsorption was remarkable while specific conductivity of exudate was more then 12.00 ms/cm. Displacement experiment showed that hydrogeochemistry actions were happened in the process of freshwater displacing saltwater with adsorption, exchange interaction, lixiviation, dolomitization and mixing action.

Key words: shallow salt groundwater, water chemical characteristics, hydrogeochemistry action, displacement experiment, inland region