The macroscopic mechanical characteristic of the rock material is integrated exhibition of the inner mechanical characteristic of this kind of material in mesoscopic view. While for the brittle rock material

the inner heterogeneity is important to its macroscopic crack form. The primary discussion on the heterogeneity of the brittle rock has been carried out with the method of evolving cellular automata. In this method

displacement

force

stress and strain are taken as basic variables of the system and the stress concentration and stress adjustment are reflected by quantitative analysis. In the macroscopic view

the brittle rock is a kind of heterogeneity material and its heterogeneity distribution is assumed as Weibull distribution. The slope parameter m is a important parameter that reflects the heterogeneity level of the heterogeneity distribution. From the numerical simulation examinations on the brittle rock material when it has different slope parameter in Weibull distribution

it can be drawn out that the heterogeneity expressed by the slope parameter in Weibull distribution is a important factor that influences the crack form of the brittle rock; and the more the slope parameter m is small

the more the composition of the rock is asymmetric

and the more the crack form is stochastic; while the more the slope parameter m is great

the more the composition of the rock is symmetrical

and the more the crack form is regular and similar to the elasticity material. It is consistent with the results of the experimentation.