The basic method for the study of grain contact probability is to record the transition sequence from one crystal or mineral species to another along a line in a thin section. The number of each type of contacts is then displayed in the form of contact probability matrix in comparison with random contact probability matrix. The data obtained in this way may indicate whether or to what extent the position of one mineral species is dependent on the position of another mineral .Generally speaking, minerals of the same species or the same generation tend to be in contact with one another .The grain contact probability can therefore be employed to distinguish mineral assemblages. A study of the grain contact probability of charnockite in Taipingzhai ahows that the major mineral facies are composed of minerals of two different generations, and this is consistent with the conclusion .reached by petrographic studies.