Tortuosity factor tau of the solid phase is an important parameter for the accurate prediction of SOFC electrode conductivity. This work investigates the effect of computational domain on tau. The results show that a computational domain with cross section area of 15d*15d (d: particle diameter) is necessary for the calculation of tau when 15% deviation is allowed. The result also validates that the anisotropic property of tau shown in the previous literatures is caused by the insufficient sample size. This study builds a framework for the further study of tau. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.