The liquid-liquid equilibrium data for the systems including benzene + n-heptane + N,N-dimethylformamide (DMF) and benzene + n-heptane + DMF + ammonium thiocyanate were measured experimentally at 298.15 K or 303.15 K and atmospheric pressure. The selectivity coefficients of the complex solvent (DMF + NH4SCN) are generally higher than those of DMF, derived from the tie-line data. For the high selectivity that is from 15.03 to 69.90 at 298.15 K or from 15.04 to 61.02 at 303.15 K, the complex solvent, DMF + NH4SCN, could be used as an extracting agent to separate benzene from n-heptane.