Abstract: Acoustic testing technology is widely used because of its low damage and simple. The broken degree is an important research content of the stability of surrounding rock. This paper introduces the basic theory of acoustic testing technology test and the method of using it to get loose zone size in detail. First of all, the elastic wave velocity of the rock should be measured in different depth by changing the probe’s place until it don’t change no longer. Then the curve of wave velocity changing with depth will be got to decision the loosened area. Finally, problems of acoustic wave test during the whole monitoring process would be found and the reliability of the acoustic test would be proved through the worksite survey.