Abstract:A testing study is presented on propagation characteristics of P wave and S wave in rock samples under dry and water-saturated conditions. The samples,including slate,biotite gneiss and granite gneiss,are all low-porosity rocks with water absorption of only 0.05%~0.2%. The acoustic parameters of rock samples under dry and water-saturated conditions are tested with ultrasonic method. Much useful information about the inner structure of these rock samples is learned from P wave and S wave. P wave velocity in water-saturated granite gneisses and biotite gneiss becomes a little higher than that of the dry ones only by 1.35%~1.97%,but becomes lower in water-saturated slates by less than 0.95%. S wave velocity in three types of rocks becomes a little higher than the that of dry ones by 0.22%~1.61%. The anisotropy of waves(P wave and S wave) velocity in slate and biotite gneiss is observed which is strengthened by water saturation,however,such phenomenon has not been found in granite gneiss. The dominant frequency of P waves becomes lower when rock samples get water-saturated,which means the high frequency part is filtered. All rock samples present obvious anisotropy of dominant frequency.