In this study, it is experimented to find factors effecting surface roughness using the system of experiments. in the mirror surface finishing system. (1) The film feed and oscillation frequency in $40{mu}m$ abrasive film, grinding speed in $30{mu}m$, and machining time in $15{mu}m$15 are the main factors effecting the surface roughness. (2) Applying the optimal finishing condition to $40{mu}m$, $30{mu}m$, $15{mu}m$ abrasive finishing film in sequence, it is possible to obtian about Ra 10 nm surface roughness on SM45C workpiece. (3) Application of the system of experments to the micro abrasive grain film finishing was very effective method in the extraction of main factor and optimal condition.