Abstract: Two important concepts in hydrogeology, groundwater type and bed rock fracture water, have been systematically reviewed, and the different groundwater classifications have been compared in this paper. There are two groundwater classification plans in the world now. The classification based on groundwater dynamic properties of the aquifer is widely agreed among hydrogeologists all around the world.Another classification is based on the rock media, which included two different plans: the classification according to the types of openings in water-bearing media, and the classification according to the rock type. Since the classification according to the type of openings (i.e., porous water, fracture water and karst water) has a good representation on the relationship among rock type, opening type and groundwater type, therefore, it has been adopted by many hydrogeolgists in China, Russia and many other countries. Based on recent data of groundwater survey in many countries, the author pointed out that although the classification according to the opening type of water-bearing media has many advantages, sortie problems still existed, such as: (1)there is no absolute co-relations among rock type, opening type and groundwater type; (2)sortie transitional rock type and the rocks with two opening types are not included in the classification; and (3)the classification does not cover all types of the groundwater. Here, the author proposed a modified classification plan, in which the transitional type, rock type and opening type have been considered together. Based on this classification, the basic concepts of bed rock fracture water have been discussed.