‘Trap’ effect of the newly developed semi-fixed abrasive tool (SFAT) plays key role in decreasing the surface damages of advanced ceramics caused by the undesirable large particles emerging in machining area. Influences of characteristics of the large particle, such as size, shape and concentration, on the ‘trap’ effect of SFAT are studied with Particle Flow Code (PFC) simulation and lapping experiments. A normalized normal force is defined to evaluate the ‘trap’ effect in PFC simulation, and surface roughness is taken as an indicator in lapping experiments. The results show that the change of surface roughness is according to the one of normalized normal force. Bigger normalized normal force is better for ‘trap’ effect and surface roughness. ‘Trap’ effect works well when the large particle is in small size, sharp shape, and low concentration. In this study, the followed characteristics of the large particle are good for ‘trap’ effect of SFAT made of 1000# SiC abrasive: size <17µm, corner angle < 60°, and concentration <18 particles per mm2.