Abstract: The main ion composition of water is the indicator which can show the lithology，climate，ecological environment of the through area. This has been widely used to identify the basic process that controls the chemical composition of the water. The research about ion chemistry characteristics and spatial distribution can be used to determine the relationship of the rivers solute geochemical sources with regional natural conditions. There are very few reports about chemical characteristics and controls at Hami Yushugou Basin，Xinjiang，China. And water resource from this river is very important for production and life of Hami. An analytical study of hydrochemical characteristics and controls of the runoff during the spring flood period at Hami Yushugou Basin were carried out in this study. In order to investigate the diurnal changing characteristics of river water chemical composition，water samples were collected at Yushugou Hydrometric Station from April 26 to May 2，2013. To analyze the major chemical ions，pH，conductivity EC，total soluble solids TDS，tools including the descriptive statistics，correlation matrices，Gibbs Figure，triangular diagrams of anions and cations were employed. The results showed that the average pH value in runoff was alkaline （8.04） in spring flood period in Yushugou Basin. EC value in runoff samples ranged from 84.5 to 168.4 μS·cm^-1. Ca²⁺ was the dominant cation，and HCO₃^- was the dominant anion. The average value of TDS was 68.84 mg·L^-1，belonging to the weak water salinity. Ca²⁺ and HCO₃^- concentration account for 74.31% and 82.07％ of cations and anions，respectively. The anionic mass concentration sequence was HCO₃^->SO₄^2->Cl^->NO^3-，and that of cationic was Ca²⁺>Na⁺>Mg²⁺>K⁺. The hydrochemical type of Yushugou basin is HCO₃^--Ca²⁺. The major ion composition，TDS，EC，pH value in runoff were little affected by instant water discharge. Affected by river gradient and flow velocity，the trends of the daily average value of ion and the daied water discharge were opposite. In Gibbs chart，the ratio of hydrochemistry ion Na⁺/ （Na⁺+Ca²⁺） was less than 0.5，the scope was mainly concentrated in less than 0.2. It indicated that the major origin of ions in runoff was weathering of rocks. Based on piper trilinear monograph，in the cationic triangle，each point was near the Ca²⁺ endmember; in the anions triangle，each point was near the HCO₃^- endmember. This means that the main process controlling the water chemistry is found to be carbonate，such as Limestone，weathering. The result of correlation coefficient between ions can partly explain the source of the ions. In result，the correlation coefficient of Ca²⁺ and HCO₃^- was the largest which showed that they had the same source，the release of calcium carbonate weathering. Other ions had their same source because of the high correlation between them. The conclusion is that the rocks weathering is the main factor for controlling the hydrochemical composition in spring flood period in Yushugou basin. And in this period，the river water is the fine source of drinking water. Thus it is important to study the water chemical characteristics in this area.

Key words: EC and TDS, ionic concentration, rock weathering, Yushugou Basin