A model of porous composite microstructures for solid oxide fuel cell (SOFC) anodes, based on spherical particle packing, was numerically studied by means of the three-dimensional particle element method (PEM), which is a discrete element method. In this model, the porous SOFC consisted of three-component particles: electronic, ionic and void particles (pores). A triple-phase boundary (TPB) was defined by the local site where the three-component phases came into contact. The length of TPB (TPB density) was calculated by the contact circle length between the ionic and electronic particles at the TPB site. In the present study, the effect of porosity could be treated in addition to the grain size of the solid phase. Because the effect of porosity was treated in detail, our numerical results were in good agreement with the experimentally measured TPB density. (C) 2010 Elsevier Ltd. All rights reserved.