A method of calculation for an accelerating jet mill nozzle profile which provides a maximum kinetic energy for solid particles at the nozzle outlet, is developed. The gas-solid flow in the nozzle is described by a well-known one-dimensional model. The effect of both solid loading and particle size on the optimal nozzle profile, as well as on the main flow parameters is studied. Distribution of particle velocities in the computed optimal nozzle is compared to that in a conical convergent-divergent nozzle of the same length. Computations demonstrated that optimized nozzles are profitable for fairly low solid loadings. The kinetic energy of solids at the optimized nozzle outlet is about 50% higher than that in a conical nozzle if the solid/gas mass flow ratio equals unity.