Abstract: In order to explore the interaction process and phenomenon between diamond and rock, the experiment of diamond indenting the rock surface in the whole process was carried out on WDW-100 electronic universal testing machine controlled by microcomputer. The breaking law of diamond pressing into rock was summarized by its test force-deformation curve. The experimental results show that the diamond with small diamond size should be selected when the diamond is pressed into hard rock, and the diamond with large diamond size should be selected when the diamond is pressed into soft rock. The diamond indentation test can provide reference for the optimization design of the drill bit.