This paper describes relationship between the grade and mechanical properties of a diamond wheel. The grade of a diamond wheel was investigated by abrasion test using diamond sticks of the same composition as a grain layer. The critical pressure and abrasion rate of diamond sticks were measured from abrasion test. Further, the number of grains on a unit area was calculated by approximating an abrasive grain to a sphere and a cube, and critical grain holding power was calculated by dividing the critical pressure by the number of grains on a unit area. The mechanical properties of a diamond stick measured bending strength and elastic modulus. Bending strength was measured by a three point bending test, and the elastic modulus was measured by an ultrasonic pulse method. In addition, Modulus of rupture was calculated from bending strength and elastic modulus. The relationship between the grade and mechanical properties of a diamond stick was considered by comparing the critical grain holding power with modulus of rupture. As the results, it found that the critical grain holding power and modulus of rupture of a diamond stick showed good correlation.