Abstract: On the basis of the change in value of motion energy of particles passing through a shock wave during the time of speed relaxation, this functional relations were set up betweenflow parameters both in front and back of shock wave of supersonic nozzle and average size of particles as well as they and specific surface area of particles, and this relations were supported satisfactorily by the experiment in this paper. The research conclusion made known that the pulverizing effect of shock wave increased with strengthening shock waves and enlarging particles size in certain range, and it was fluctuate change with varying Mach number. However, shock wave did not make the particles size vary too much, on the contrary, it made the jet speed of nozzle reduced, and also made the intensity of impact pulverizing reduced , it is disadvantage to improve the comprehensive grinding efficiency of a jet mill. Hence, shock wave should be eliminated as possible as in the design and operation for a jet mill.