During core drilling, blockage and sticking often occurs when conventional three-wing reaming bits are used for reaming in broken strata such as gravel (boulder), which results in low reaming efficiency. For this purpose, a reaming bit with guiding and gauge protection functions was designed, and was applied in a comprehensive geological hole in Lingwu, Ningxia, with good reaming effect, and the average reaming footage up to 3.5m/h. The reamed hole was highly coaxial with the original hole, and had a regular gauge, leading to smooth casing running. The Quaternary broken formation was effectively separated to ensure smooth performance of subsequent core drilling and geophysical logging.