The three-dimensional coordinates of rock fracture surface was obtained by three-bending tests and the laser scanning of surface.The fractal characteristics of coarse fracture surfaces of marble and granite was investigated on the basis of fractal dimension calculation theory-surface covering method.The results showed that the fractal dimension and intercept can be used as geometrical describing p arameters of coarse rock fracture surfaces.The fractal dimension denotes rough d egree of surface and fractal intercept characters its waviness,the two complemen t each other.But for rough characteristics the separating degree of fractal dime nsion is less.