The SAS’ nozzle two-phase flow computer program has recently been revised to achieve a higher .accuracy in calculating thrust characteristic and behavior of particle streamlines. Alumina particles had been gathered in lots of motor firings over a wide range in scale. The particle size distribution characteristics were obtained and the resulted particle sizing equation in terms of the mass averaged particle diameter D43 is quite close to that employed in the improved SPP, i.e., D43 is a unique function of motor throat diameter. Subscale motors containing highly aluminized propellant were fired, whose nozzles were designed to have significant amount of particle impingement and then severe erosion at the exit lip. The nozzle eroded locations were used to verify the computational accuracy of impingement location prediction. It has been shown that the improved two-phase flow program can well predict the particle impingement location by assuming an appropriate particle diameter DpIMP, which is proportional to D43. The proportional coefficient is rather universal.