In this research the abrasive flow finishing process (AFF) of AISI H13 hot work steel was studied and the effects of various process parameters such as flow pressure (extrusion pressure), abrasive particles densities, abrasive particles sizes and the first quality of surfaces on variations of surface roughness and material removal have been investigated. The results showed that increasing the density of abrasive particles leads to increase in variations of surface roughness and material removal. Increase of extrusion pressure from 4 to 6 MPa causes the increase in variations of surface roughness and material removal and from 6 to 8 Mpa leads to decrease in the two latter. Electron microscopic results showed that increase of finishing process time over 4 hours causes a detrimental effect on the surface of the specimens, as a result of penetration and stabilization of abrasive particles in the form of broken particles. Also according the results of this paper, increasing the size of abrasive particles leads to higher variations of surface roughness and material removal, and this process is more effective in finishing of rougher surfaces.