[en] The K-classifying testor method is a discriminating method of two groups, which is able to process the qualitative geological data. For the continuous variables obtained by geophysical and geochemical prospection an optimum discretization which may keep the information contained in them as much as possible is proposed. The formulae for calculating the K-mode distinguishing weight of every significant character, the distance between two objects and the criterion for discriminating unknown objects are given. In the end of this paper we present a case history of applying this method to classify twenty one granitic batholithes in southern China