The 1H-nmr lineshapes of H2O in the solution containing Al3+ ion have been measured as a function of temperature and H+-ion concentration. Above [H+] = 0.06, the lineshape were analyzed by the uncoupled two-site exchange model. From the proton exchange rate between hexaaquaaluminium ion and bulk water as a function of H-ion concentration. These kinetic data could be fitted to a following linear rate law; that is; 1/τ = k1/12 + k2[H+]/6. The following proton exchange parameters were obtained; k₁^{298 = 38.5s-1 ΔH1≠ = 42.9kJ mole-1 ΔS1≠ = -48.6J mole-1 K-1 k₂298 = 172s-1mole-1 ΔH2≠ = 27.8kJ mole-1 ΔS2≠ = -90.3J mole-1 K-1 These activation parameters are indicating an associative interchange, Ia, mechanism for the acid-hydrolysis of hexaaquaaluminium ion and the proton exchange between the hydration spheres of Al3+ and H+.}