Based on the characteristics of movement of karst groundwater, this paper provides a concept model of the rise and propagation of karst groundwater pressure wave. By using the grey system theory, the authors propose a karst hydrological model including calculation of hydraulic response time between spring discharge and precipitation, and a response model of spring discharge to precipitation. The results reveal that the karst groundwater circulation is a process of rise and propagation of pressure wave. Karst spring discharge is the response of groundwater system to regional precipitation. The hydraulic response time is an important parameter reflecting the characteristics of a karst groundwater system.