This paper reported the thermodynamics of extracting Re(Ⅶ) with the extractant of N816 (R3N) in the H2SO4 system. The equilibrium molalities of ReO-4 in the extraction R3N (org) + H+(aq) + ReO-4 (aq) = R3NHReO4 (org) were measured at ionic strengths from 0.1 to 2.0 mol.kg-1 in the aqueous phase containing Na2SO4 as the supporting electrolyte and at constant initial molality of extractant in the organic phase at temperatures from 278.15 to 303.15 K. The standard extracfion constants K at various temperatures were obtained. The working equation was obtained as lg K = 2.819 + 905.44/T- 0.00349T. Thermodynamic parameters for the extraction process were calculated.