Abstract: The groundwater system in karst region is the basic water system in Southwest of China karst mountain. The classification of karst groundwater system is a foundation for estimation and use of water resources there. According to the outcome condition of karst water, 3 620 karst groundwater systems are divided, including 1 179 subterranean streams, 1 152 karst spring systems, 562 concentrated drainage systems and 727 decentralization drainage systems. Being based upon the outcome condition of terrain in karst region, five types are divided： bare karst （2 324）, bare-covered karst（108）, covered karst（275）, bare-buried karst （88）. Except decentralization drainage karst water system, there are 26 karst groundwater systems with the catchments bigger than 1 000 km^2 in area. In subterranean stream systems, there are 1 049 systems with the catchments between 10 km^2and 500 km^2 in area that accounts to 88.97% of the total, 711 ones with the catchments smaller than 100 km^2 in area that accounts to 60. 3%0 of the total. In karst spring systems, there are 814 systems with the catchments smaller than 50 km^2 in area that accounts to 70.66% of the total. In concentrated drainage systems, there are 303 systems with the catchments between 100 km^2 and 500 km^2 in area that accounts to 53.91% of the total. The result of runoff statistics shows that 286 groundwater systems is more than 1 000 L/s in runoff that accounts for 11.2% of the total and 630 ones are between 50 L/s and 500 L/s in runoff that accounts for 63.73% of the total.