An SRF plant which can produce 100 ton/month of SRF, one of the largest manufacturing plants in Korea, was investigated in this study. The actual operated SRF yield at 21.7 % that showed a lower yield than expected; originally designed value was 25.0%. The cause of these results was the difference between characteristics of MSW applied to this plant originally and that which was actual incoming. The MSW led to decrease the separation efficiency of the mechanical treatment process. Thus, each element of the facility was modified. After modification, the SRF yield increased to 30.9%, whereas the physico-chemical properties of SRF were satisfied with domestic standard of SRF regardless of modifying MT facilities.