Abstract: In the construction of large diameter drilling in coal mine, the construction method of grading reaming is usually adopted. Therefore, the selection of large diameter reaming bit is directly related to the construction efficiency of large diameter drilling. Taking the large diameter borehole engineering in Hanglaiwan Coal Mine as an example, this paper introduces the construction technology of large diameter drilling and the optimization of the bit, which has accumulated precious experience for the same type of drilling construction in the later period of northern Shaanxi province.