The paper studied the formation and evolution mechanism of hydro-geochemistry of groundwater,which is important for the assessment of water quality and the sustainable utilization of water resources.It used the analysis results in unconfined aquifer and confined aquifer from 1981 to 2003 in Changling county,and analyzed the effect of hydro-geochemistry of groundwater and evolution law of water quality.The paper collected 198 monitoring points of water quality so as to analyze and deal with,and used Piper graphic method, Gibbs graphic method and ion ratio analysis method to research.The results demonstrate that the groundwater is mainly affected by cation exchange function and halite dissolution, among that anions HCO-3 are the dominant components of water and the cations are Ca2+ and Na+. The groundwater has the property of alkalescence and high hardness. The dominant hydro-chemistry type of water is HCO3—Ca in the unconfined aquifer, whereas that is HCO3—Na in the confined aquifer. The hydro-chemistry type of groundwater is more stable.The water quality is less affected by human activities.