Effect of large amount of dispersed particles on ultra-fine grain evolution by multi-directional forging (MDF) was investigated. For that purpose, austenitic stainless steels containing about 1 vol.% of second phase particles, which diameter ranged from 8 to 140 nm, were MDFed at 673 and 873 K to strains up to epsilon = 6 at maximum. Microstructure with nodes of dislocation walls or boundaries was gradually developed as strain increased. During MDF process, the particles transformed from coherent to incoherent ones. By this transformation, flow stress decreased in spite of substructural evolution including fine grains. However, fine-grain evolution seemed to be stagnated by the presence of the fine particles when compared with the result of plain Fe-Ni austenitic steel. Though disorientation became larger with increasing strain, the evolved boundaries/dislocation walls possessed "foggy" appearance. This indicates that sharp boundary evolution was impeded by the presence of large amount of particles. While ultra-fine grain evolution was not sharply took place even at epsilon = 6 in some samples, the apparent grain size of the ultra-fine grains specifically divided by foggy dislocation walls, which included large disorientations, was about from 0.2 to 1.0 mu m in average depending on particle distribution. The effect of stagnation of the microstructural evolution was more obvious in the samples containing finer coherent particles.