This paper concludes that groundwater age is important in assessment of groundwater renewability, recognizing groundwater movement and mass transport process, and constraining parameters of groundwater model based on many case study examples both at home and abroad. Whereafter, the paper indicates that groundwater dating is disturbed by human activities and discrepancies of dating results are induced by using different methods of groundwater dating, as well as affected by mixing processes of groundwater and atmosphere-water-rock interactions naturally. The paper also points out that the ages of tracers in groundwater samples measured do not veritably represent those of groundwater itself, and factors influencing groundwater dating due to processes discussed above should be considered adequately.