Understanding hydro-chemical characteristics and formation mechanism of surface water and groundwater is very important for protecting and utilizing groundwater resources rationally. Based on the sample of Kuihe river water and its coastal groundwater, methods including descriptive statistics and three lines Piper diagram of major ions were used to analysis the water’s hydro-chemical characteristics and forming effect. Research results show that: (1)In the term of space, the hydro-chemistry type and its concentration in Kuihe coastal groundwater from different sections has different characteristic and so it is in Kuihe water. In the term of time, Kuihe river water and its coastal groundwater in one section also have different features when it is in wet season and in dry season. (2)The advantage effects caused by groundwater hydro-chemistry types from different sections are also not the same. The groundwater’s hydro-chemistry type of Xucun section is greatly influenced by leaching effect. The effect of evaporation and concentration is stronger at Huangqiaozha section than the other two sections. As to Shiqiao section, the positive ion alternately adsorption plays an important role. And human activities have more or less influence on groundwater near Kuihe River in each section. (3)The advantage mechanism formed by Kuihe river water’s hydro-chemistry type is evaporation and concentration effect. Also, the dissolution of carbonate minerals in riverbed also has greatly effects on the formation of ion composition characteristics. At the same time, human activities such as setting brake to store water and irrigation also have a huge impact on the Kuihe river water chemical evolution.