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 t...