The effect of operating conditions on the performance of a CTAB modified resin column used for the treatment of steel rolling oily wastewater was investigated. The influence of flow rate, influent oil concentration, fixed column height and influent pH was studied. Experimental results showed that several processes were involved in oil removal from rolling oily wastewater, i.e. emulsion breakdown, coalescence and adsorption. More than 95% of oil content in the influent stream was removed by the modified resin column and it increased by 15% compared with the unmodified resin column.