Viscosity and density for the ternary solution of hexanedioic acid dissolved in poly(vinyl alcohol) (PVA) + water at the temperatures (293.15, 298.15, 303.15, 308.15, and 313.15) K are reported in this paper. A linear relation between the viscosity and the concentration of hexanedioic acid is observed, and the viscosity B-coefficient is extracted. The activation free energy for the viscous flow of the solution is found from the slope of the linear equation by using the Eyring-Feakins equation. By investigating the concentration effect, we have found that with the increase of PVA concentration the activation free energy of viscous flow first decreases and then increases. This implies that PVA promotes the diffusion of hexanedioic acid at lower concentration but demotes the diffusion of hexanedioic acid at higher concentration.