Based on the petrophysics theory, the authors measured the samples from the Silurian-Devonian Tertiary formation in the Tahe oilfield for ultrasonic compressional and shear wave velocities in rocks under the conditions of various temperatures, pressures and densities. The results show that the compressional and shear wave velocities show linear relationship in mudstone and sandstone fully saturated with water and oil. The rock velocities increase with the increasing temperature and pressure, whereas the rock velocities decrease with the increasing porosity in dry core samples and sampls saturated with water. According to Shuey's approximation, AVO forward modeling was conducted on the basis of petrophysical parameters. It is indicated that the AVO abnormal responses from Silurian-Devonian reservoir property belong to Class One in the Tahe orefield.