This paper presents an attempt to model the dependence of porosity on particle size distribution for wet coarse spheres. The model is developed by extending the linear packing model originally proposed for the packing of dry particles. Therefore, emphasis is mainly given to the determination of the two unknown factors in the model: the initial porosity (the porosity of monosized particles) and the interaction functions describing the effect of the mixing of bi-sized particles. While the initial porosity can be estimated by the equation formulated in our previous work, in this-work, the interaction functions are quantified as a function of three variables: moisture content and absolute and relative particle sizes based on the experimental results of binary mixtures of wet particles. The applicability of the proposed model is verified by the reasonably good agreement between the measured and calculated results for various packing systems composed of wet spherical glass beads with discrete or continuous size distributions.