Abstract: Micromechanical damage evolution characteristics for a variety of particulate reinforced metal matrix composites(PRMMC) were investigated in ductile fracture. A weakest chain model of micro-damage was proposed, and the relationship between the global damage variable and micro-damage mechanism was established. The influence of the reinforcement size and the volume fraction on damage evolution was investigated for commercially pure aluminum and aluminum matrices reinforced with SiC particles. The effects of matrix heat treatment on the damage evolution were analyzed as well. It is concluded that the damage evolution could be expressed in a power-law form and the weakest chain model of micro-mechanical damage is able to investigate the damage mechanism. A very good agreement is obtained between the calculated values and experimental data for ductile damage evolution.