Three exploration boreholes have been completed in the Cangzhou Salt Mine general survey project， with the drilling depth ranging from 3000 to 3451m， and the total coring length of 3791m in Paleogene plastic-brittle formation. Based on the drilling characteristics， the proper bit selection principle was determined for the elastic-plastic interval and brittle interval in the work area. After several tests and improvements， 15 kinds of bits belonging to three categories-carbide， PDC and Balas were used. Comprehensive analysis was carried out according to the bit structure， rock fragmentation mechanism and application effect， and three kinds of bits of H-4-Ⅱ， F-3 and F-6 were optimized. These bits had high efficiency and good coring quality when drilling in Paleogene strata， which are suitable for the geological conditions in the work area， and can be recommended to popularize and apply in this area.