There often exist several kinds of split planes in a slope. Could these planes delevop into sliding surface, it depends on several factors, for example, stress state, properties, shape and development density of the split planes, and so on. Through analysing these slide planes, stress,state, and cluster analysis, we determine several groups of the latent slide planes, then we classify and analyse these groups of split planes in slope. The primary method is that each sample of each group (split planes or latent slide planes) is regarded as one kind. According to distance or similar coefficient between the samples, we merge two kinds, which are more similar, into one kind, and calculate the distance of new kind to other kinds, and so on, finally, merge into a kind which we need, and determine one kind of split plane which may possibly develope into active sliding surface.