Abstract: There are intrinsic difference of work mechanism between diamond compact bit and impregnated diamond bit. The work mechanism of diamond compact was theoretically researched, on the basis of the force on diamond compact during the cutting course, then the results of theory calculation and experiment data were juxtaposed.The results showed that within a certain range, the mechanical speed increases with the cutting depth of PDC in rock, while the depth of cut depends on the rock by the PDC cutting angle of the axial load and other parameters. And with the increase in speed or axial load, dynamic load coefficient B should take smaller values, so the design of diamond cutting tools and of the drilling parameters will be promoted through the results analysis.