Three types of cubic cell models containing one void, two voids and nine voids respectively are used originally to investigate the problems of void size effects on the damage evolution of ductile materials. The cells have equal initial void volume fractions f 0 (0.01%), but the different void sizes with relative radius 2.0,1.6,0.96 and different spaces. The stress state parameter ( T =1/3,1,3) represents the loading conditions of uniaxial tensile round smooth bars, round notched bars and crack tip fracture process zones. The results are obtained by using FEM software ABAQUS 5.8(1998) and discussed completely. By comparing the results, it is found that the relative void volume fractions f/f 0 and the stress carrying capacity of material with different void sizes can be very different. For the larger void, the ratio f/f 0 increases faster and the stress carrying capacity drops more rapidly especially when the stress state parameter and higher. It means that the ductile materials with larger, voids can fail earlier than those with the smaller ones. The void damage evolution processes accompany the plastic deformation of materials. The difference of void sizes may change the ways of macro scope and meso scope plastic deformation of materials. The void size effects on damage of ductile materials may not be ignored. If initial different void sizes refer to inclusion and second phase particle sizes in real materials, it will be beneficial to increase the strength of materials by decreasing the inclusion and particle sizes in metallurgic processes.