Abstract: Fractured rock mass fractal theoretical model was construct. Block composition and porosity fractal characters of fractured rock mass were studied by using fractal theory. Block fractal number,porosity fractal number and porosity of fractured rock mass, as well as their relationship were studied and formula for calculating them were obtained When statistics are accurate enough, block fractal number is almost equal to porosity fractal number, which means that statistcal fractal dimension is almost equal to theoretical model fractal dimension otherwise, block fractal number is a little larger than porosity fractal number, which means statistical fractal number is a little larger than theoretical model fractal dimension. By applying the calculating method of fractal theoretical model to the main sgaft in Xincheng Gold Mine,the result shows that its theoretical model fractal dimension D_t is 2.4 and porosity is 22.6%.This result Played an important role in the design calculation of the grouting reinforcement project's scope, the strenth of grouting reinforcement material and the amount of grouting material. The result has been also proved to be correct by the practice.