Abstract: Taking Lirang tunnel of Liang-Zhong Expressway in Chongqing city as an engineering background，based on the field joint investigation by scan line，the distribution density function of joint production is obtained; and the fractal distribution law of joint spacing and trace length is analyzed from the viewpoint of fractal geometry. In addition，the fractal dimension D from the distribution of joint spacing and trace length and fractal distribution probability density function can be derived. Based on these work，Monte Carlo stochastic simulation theory and Matlab software are adopted to obtain simulated joints data. Finally, a discrete fracture network(DFN) model which could reflect the distribution characteristics of the joints is established. The results of the study show that：the fractal distribution contain more information about the joint spacing and the trace length distribution than other distributions; and it is more close to the actual distribution. Fractal dimension D reflected the distribution of joint spacing and trace length in its variation range，and the fractal dimension D is determined depending on the ratio of the number of small spacing，the number of small trace length to the total number of joints. This study results provides a new method for the construction of the network model of jointed rock mass.

Key words: jointed fractured rock mass, joint spacing, joint trace length, fractal distribution probability model, discrete fracture network(DFN) model