Abstract: We put forward a risk definition of groundwater systems on the bases of summarizing previous studies in groundwater risk analysis.Characteristics of groundwater systems are reviewed in detail,and risk effect factors in a groundwater system are analyzed and highlighted.The risk factors are then resumptively classified into three categories:Uncertainty of natural phenomena,social uncertainty and limitations in human cognition.Discussions on risk analysis methods are also given.For the issues and deficiencies on the subject,we highlight four aspects to improve the risk analysis of groundwater systems.These aspects include developing basic theories and expanding research methods,properly selecting the risk analysis approaches to addressing different concerns,combining risk probability and its loss,and studying on risk of risk analysis.