On the basis of understanding the hydrogeological conditions in Guangzhong Basin, in order to reveal the formatiom mechanism of chemical field of groundwater,the paper analyzed the chemical feature of groundwater and disscused its formatiom mechanism .The results show that the types of water chemisty, salinity and hardness have horizontal distribution characteristics, but they have own''s characteristics due to the constrains of the geological and hydrological. The distribution of iones content has a certain contact with pH value, salinity, hardness and water chemical types. The change tendency of iones is significantly constrained by the salinity, and the dynamic field of groundwater controls the chemical field.