The extraction process of rhenium was investigated in the room-temperature ionic liquid 1-pentyl-3-methylimidazolium bis((trifluoromethane)-sulfonyl)imide ([C(5)mim][NTf2]) containing N235. At ionic strength ranging from 0.2 to 2.0 mol.kg(-1) and temperatures ranging from 293.15 to 318.15 K, the molalities of perrhenate in the aqueous phase were obtained at an extraction equilibrium. The standard extraction constants K-0 at diverse temperatures were gained by the Pitzer polynomial approximation method. Thermodynamic characters for the extraction procedure were calculated.