Abstract: In order to solve the problems associated with drilling bore diameter selection and layout of drilling in the local outburst prevention measures of Zhujixi Coal Mine, combined with the actual situation of 11-2 coal seam, we use predict index cuttings method to measure bore diameter of 75 mm,94 mm,108 mm and 127 mm and the effective drainage radius was 1.1 m, 1.2 m, 1.4 m and 1.5 m respectively. The result is that the drainage radius increases with the bore diameter and gradually becomes larger, but the increasing amplitude decreases gradually. Therefore, in the implementation of drainage borehole outburst prevention measures, selecting the appropriate aperture is the key technology to achieve the optimal effect of outburst.