Abstract: The variability in orientation and inclination of drill for seepage control (reinforcement)engineering is determined by the anisotropy of permeability of jointed rockmass and random of permeability ratio,which also indicates that the assumption that the permeability of rockmass is isotropic is not actual in the design of seepage control.The vector of drill for seepage control should be determined from the joint width and orientation along which the permeability and its ratio are larger.