Abstract: Based on K-S test， a new method was proposed to identify statistically homogeneous regions in a fractured rock mass by considering trace length of joints. The cumulative frequencies of each attribute of contrasting samples， the K-S statistical quantity and the K-S critical values were calculated to validate the significant difference between the comparative samples， based on which， the structural homogeneity of fractured rock mass was divided. This method was used to analyze the effect of the trace length on statistically homogeneity division in the fractured rock mass at two adjacent adits in different weathered zone at the Maji dam site on the left bank of the Nu River in Yunnan province. It was calculated that the rock mass at two adjacent adits shows statistical similarity in the lower limit of weak weathering， slightly weathering and fresh rock zones，and can be divided into statistically homogeneous areas， however it shows no statistical similarity in the upper limit of weak weathering. The rock mass at a single adit shows no statistical similarity in the every division of weathering. In addition， the proposed method can be applied to identify the dividing of joint samples with small sizes.

Key words: fractured rock mass, statistical homogeneity of rock mass structure, K-S test, stochastic mathematics, trace length of joints