Abstract: The application of a filter-based model(FBM)for the computations of cavitation flow is studied based on the flow around a cascade hydrofoil. With reference to the largest grid size of the refined region near the hydrofoil, four filters were selected in the FBM model. Through comparison with the results of the experiment and the standard <em<κ-ε</em< model, the effects and selection of the filter size were studied at the aspects of cavity shape and drag prediction. The results shown that the turbulent viscosity correction by the filter function is mainly done at the region of cavity shedding in the rear part of the hydrofoil, and the correction is increased with the decrease of the filter size. Considering the resolving capability of the grid for the turbulence scale, the filter size is proposed to be a value a bit larger than the largest grid size of the refined region.