Abstract: For process of optical components having defects such as sharp projections, pits and scratches at the micro, abrasive waterjet impinging with low mass concentrations is proposed. Starting from the elastic contact, the critical velocity of plastic contact between components and waterjet particles is deduced. The critical impinging velocity of ductile to brittle transfer is introduced. Thus the velocity range of the ductile removal is clearly defined. Combined with specific parameters, K9 and fused silicas velocity range of the ductile removal are simulated. Using the single particle impinging removal model, these two materials' impinging removal in ductile removal manner is simulated. The results show that the critical velocity of plastic contact for fused silica is higher than K9s, but the velocity of ductile to brittle transfer is reversed. Thus, the velocity range of ductile removal for fused silica is a subinterval of that for K9. The impinging removal of these two materials increases with the increase of impinging velocity. However, the harder fused silica is less resistant to impinging than K9 and it is easier to be removed by impinging.