Abstract: An ultrasonic wave experiment of six coal samples from 15^# coal strata in Yangquan coal mining area was conducted under normal temperature and variable pressure condition in this paper, and the effect of confining pressure on coal seam wave velocity was analyzed. Results show that both of the P-wave and S-wave velocity of the samples increase with the confining pressure and have close second phase correlation with the pressure. The increased amplitude rate of coal samples with different fracture development degree is different with the increase of the confining pressure; there is a good linear positive correlation between P-wave and S-wave under different confining pressure conditions. By the data analysis from variable-azimuth ultrasonic testing, the coal seam has an obvious S-wave velocity anisotropy, and the direction of main fractures of this coal seam is determined.