Due to the ignorance of the effect of the water–vapor interface on the cavitation flow field, the standard k–ε turbulence model (ST model) may overestimate the turbulent viscosity. It is unable to simulate cavitation shedding, especially at small attack angles of a hydrofoil. In the present investigation, a turbulent viscosity correction model is proposed to dampen the turbulent viscosity at the water–vapor interface. Cavitation flow around a NACA0009 truncated hydrofoil with a 2.5 deg angle of attack is used to demonstrate the effect of correction. The results show that the interface effect-based correction model (IE model) can both predict the pressure distribution on the suction surface of the hydrofoil with experimental data and the re-entrance jet in the leading-edge cavitation shedding. The region of the IE model influenced concentrates on the water–vapor interface and intensifies the vortex strength, which directly enhances the formation of a horseshoe vortex. The reduction of turbulent viscosity by the IE model reduces the resistance to the development of a re-entrance jet. The shear stress plays an important role in the shedding of the attached cavity bubble. The increase of shear force in the leading-edge cavitation occurs with the re-entrance of water and the main shear flow concentrates on the middle of the cavity bubble. This paper therefore presents a new method of numerical simulation of cavitation flow in engineering applications.