[Objective]Gannan area in the upper reaches of Dongjiang River Basin is a typical water shortage area in China. The distribution of acid groundwater intensifies the lack of regional domestic water. [Methods]This paper selects Xunwu area in the upper reaches of Ganjiang River Basin as the study area, systematically collects shallow groundwater, analyzes the pH value, spatial distribution and hydrochemical type of acid groundwater by using the methods of Hydrochemistry and mathematical statistics, and discusses the control effects of acid rain, aeration zone medium, sulfide mineral dissolution, hydrochemistry and human action on acid groundwater. [Results]The pH value of groundwater in the area is concentrated between 5.0~7.0; The correlation between spatial distribution and geomorphic characteristics is obvious: middle and low mountains < hills; The hydrochemical characteristics of different groundwater are mainly low salinity and weak acid neutralization ability. In pH value, HCO3 type (6.0) > HCO3-Cl type (5.05) > SO4 type (4.8) > Cl type (4.5); Among the pH values of groundwater types in different media, pore fissure water of clastic rock > pore water of loose rock > fissure water of metamorphic rock > fissure water of magmatic rock. [Conclusions]Acid rain and the dissolution of CO2 gas is the main material basis of H+ source; Acid neutralization capacity is the main environment affecting the formation of acid groundwater, and human factors are also an element that can not be ignored. The research results have a guiding role in understanding the causes of acid groundwater, rational utilization and protection of groundwater resources in this area.