Abstract: Fracture spacing in different directions can not only reflect heterogeneity and anisotropy of rock mass， but also can reflect the spatial distribution characteristics of fracture， therefore， a method that demarcate structural homogeneity according to fracture spacing is proposed on the basis of random mathematics. The method is successfully applied to the analysis of structural homogeneity in an adit of Songta hydro-power station. It is proved that there exists the spatial effect when dividing the structural homogeneity by changing the space of the compared samples. Compared with the acoustic test curve of rock mass， it is shown that the division of structural homogeneity with the spatial effect considered is consistent with the on-site situation.

Key words: structural homogeneity, fracture spacing, random mathematics, correlation coefficient, spatial effect