Abstract: Experimental results indicate that the crack propagation path of a brittle mate-rials is irregular and tortuous,and fracture surfaces are roughness,which behave as fractal. Applied fractal geometry,the author derives formula of fractal kinematics of the crack prop-agation in brittle materials.The correlation of dynamic and static fracure toughnesses withcrack velocity,crack length,microstructure parameter and fractal dimension is obtained. From equations of estimating crack velocity and fractal dimension de...