Abstract: The substances separation in the food waste pretreatment stage has a great influence on the whole processing technology. If the sorting is not in place， there will be more impurities in the slurry， which will lead to the increase of equipment failure rate， pipe wear and other problems. The separation unit in the food waste pretreatment system was studied by reducing the rotating speed and feeding frequency of large substances separator. The results showed that with the decrease of rotation speed， the effect of sorting out large pieces of glass and ceramics could be achieved， the water content of the separation material had been increased but not obvious， the oil content rate would be increased， and there were some problems such as separating some organic substances， but there was no phenomenon of large amount of slurry being separated. With the increase of feed frequency， the content of separation material increased. The feeding speed had little influence on separation material composition and the overall data was stable.