In the entrainer screening for separation of isoparaffins and naphthenes (C-9-C-14) by extractive distillation of D60 oil, various single entrainers and mixed entrainers were used and studied. Sulfolane was the most selective entrainer as a single entrainer was applied and the relative volatility of isoparaffins to naphthenes reached 1.648 as the sulfolane to oil ratio was 5:1. Both mixed entrainers of sulfolane + triethylene glycol and sulfolane + dimethyl phthalate show good synergistic effect, whereas a mixed entrainer of triethylene glycol and dimethyl phthalate shows little synergistic effect. The most selective mixed entrainer was a mixture of 50 vol % of sulfolane and 50 vol % of dimethyl phthalate, the relative volatility of isoparaffins to naphthenes reached 1.835. Results from the experiment in an extractive distillation column show that isoparaffins concentration of more than 95 wt % in the isoparaffins product and naphthenes concentration of more than 94 wt % in the naphthenes product are achieved.