In this paper, using the ultrasonic experiment of sandstone under uniaxial compression about P·S. wave, the variations of Vo Vs (velocities) Vp/Vs, Ap.As (amplitudes) As/Ap, initial frequency and midium transfer function before the crack of sandstone of high porosity have been studied The results are:1. Variation of Vp. Vs and Vp/Vs is the same as that of granite.2. Variation of Ap/As has taken place.3.The low frequency has increased.4. V ariation of medium transfer function has taken place 5 2-d P wave has been engendered.