The invention relates to a method for detecting the critical cutting depth of a hard and brittle ceramic material. The method comprises the following steps of: (1), firstly, sticking a thin gasket on a basal disc, taking a polished hard and brittle ceramic material slice with an ultra-smooth surface and without scratches as a work-piece slice, and putting the work-piece slice on the thin gasket to be stuck, so that the work-piece slice forms a tiny slope; (2), enabling the particle size number, processing load, processing rotation speed and processing liquid of a grinding disc to be the same to those under experimental processing conditions, wherein abrasive particles form micro cutting marks from shallow to deep on the surface of the work-piece slice during processing; and (3), tracking and observing the cutting marks of the abrasive particles in a processing transition area by adopting a white light interferometer, finding out the cutting marks, with obvious plastic and brittle conversion characteristics, of the abrasive particles, finding out a first fragmental crack, and carrying out two-dimensional outline analysis on the first fragmental crack, wherein the cutting mark depth of the fragmental crack is defined as the critical cutting depth of the hard and brittle ceramic material. The method disclosed by the invention has the advantages of high detection precision and good reliability.