A flow intensification model was proposed for calculation of the initial collector efficiency of a granular filter. In this model, the flow acceleration within voids of granular media is taken into account with an intensification factor β. Simple physical argument gives an estimation of β, which should be close to 1/ɛ. Creeping flow is assumed and Happel model is used to represent the granular media. After obtaining the flow field, the initial collector efficiency η0 is calculated from trajectory analysis and compared with experimental data. The reasonably good agreement between the theory and experiments suggests that the current model is physically plausible and potentially useful for granular filter performance prediction if further theoretical development is implemented.