A new method for fabricating the thin-walled diamond core drill by brazing technology and the optimum grain distribution was proposed in this paper. Machining performance experiments have been carried out, including contrast tests about drill life and machining efficiency for the thin-walled monolayer brazed diamond core drill and electroplated one. The testing results show that thin-walled monolayer brazed diamond core drill has certainly super-excellent machining performance. Wear mechanism of diamond grits was studied in those drilling processes. No pulling out for the thin-walled monolayer brazed diamond core drill grits is the key factor of its longer life, and the optimum grain distribution and less wear flat of grits during drilling decrease the drilling spindle direction force, and improve the machining efficiency. It can be concluded that the new technology can radically improve the bonding strength at the grains interface, and make every grain effective during drilling.