In this paper,research on defects of geomembrane (GM) used in practical engineering in China and abroad is summarized and evaluated from the aspects of geomembrane defect types and test methods,theory of defect analysis and defect calculation model,principles and measures of defect prevention,cushion layer properties and interface flow,the rate of leakage under different contact conditions and cushion layers,and factors of leakage induced by geomembrane defects. Analysis shows that,due to the complexity and uncertainty of geomembrane defects,current research is mainly based on experiments,accompanied by theoretical analysis and numerical simulation,producing different results from the theoretical results. Some key problems related to geomembrane defects that require further research are put forward so that an overall recognition and effective control of geomembrane defects can be realized as early as possible.