Drilling construction was difficult in Qinghai Yemaquan mine, diamond bits were replaced frequently during exploration, which caused low bit service life, long construction period and high cost. All these were due to the unclear drillability in the mine and the adopted diamond bits did not adapt to the drilled strata. By the on-site survey, rock sampling and the indoor test, including thin section analysis and XRD test, the quartz content, grain size of quartz, feldspar content and feldspar granularity etc. were obtained to determine the rock drillabiligy. Based on these data, the diamond bits were selected. The outdoor test results show that the selected diamond bits work well with high performance- price ratio.