In the groundwater flow modeling, the optimal parameter zonation is still an important problem and is also a difficult problem to deal with because of the spatial variability of water-bearing media. In this paper, the concept of preferential flow in soil study is discussed and extended into the karst-fracture media. The controlling mechanism of the preferred plane on groundwater is systematically analyzed and superior indexes for making certain optimal parameter zones in the karst regions of northern China are put forward. The parameters are calculated by the finite element method. This idea has been applied to the analysis of water flow controlled by preferred fractures in the Jiaozuo Mine and the result is in agreement with factual geological conditions. The idea is also applied to the modelling of groundwater resources in the Xuzhou karst area. The calculation results show that it is possible to make certain optimal parameter zonation to combine the analytical method of preferred plane with geological conditions. This conclusion is of importance in the study of preferred flow and the evaluation of groundwater resources in the karst-fracture areas in northern China.