Abstract: On the basis of the observed field data of water head, a new type of hybrid genetic method was proposed for the inverse problem in which the relative coefficients of permeability are regarded as the unknown parameters.The relative coefficients of permeability of rock foundation under a gravity dam are successfully obtained, as well as the flexibility of applying hybrid genetic method in the practice is proved. The distribution of the water head and uplift pressure in a typical dam section are further predicted in order to verify the rationality and reliability of the proposed method. 