A method for determining the grade in the vitrified wheel in terms of the acoustic emission (AE) is described. Correlations between the grade and the amounts of AE pulses emitted from the specimen surface which is indented with either Vickers' or spherical indenter are investigated. Experiments are performed for eight different wheel structures at room temperature. As for the sphere indentation, a clear correlation between AE total counts and the grade obtained by conventional technique is found, if the small amounts of indentation load is subjected. Though total ringdown counts for the Vickers indentation are widely distributed, reflecting the statistical nature of the fracture process in a microscopically heterogeneous media, mean values should give the appropreate results. While these examples tested are not widely ranged in the grade, they do show availability in applying the AE technology to the determination of the degree of the wheel grade.