The most difficult problem of drilling in hard and compact rocks is that drilling efficiency is very low. In this case, a new type of hot-pressing diamond bit was developed. By changing weakly-bonded materials and adding strengthened granular graphite to bit matrix, the diamond exposure of bit was improved. Based on the tests, the relation between diamond exposure and graphite size, graphite content in matrix and strengthening degree were obtained. Field drilling results showed higher diamond exposure; penetration rate was 1.2m/h; service life exceeded 20m.