Abstract: In this paper the drillability of frozen clay is analyzed by using the elastic wave theory under an impact load. The main factors affecting the drillability of frozen soil are determined, namely temperature, wave velocity, impact inductility and chiseling specific work. The drillability tests of frozen clay are carried out under the seven different temperatures. The results show that it is appropriate to define drillability using the chiseling specific work factor because it has a good relationship with drill hole and can reflect the drillability of frozen clay quite well. The test results provide a good guideline for drilling in frozen soil.