Anodic microstructure influences overpotential characteristics and the optimization of the microstructure for given anode materials and operating conditions is challenging. In this study, we have tested enormous number of microstructures of Ni-YSZ cermet anode using the porous structure simulator developed previously. As a result of overpotential calculations, we found anode structure giving superior overpotential characteristics with different microstructures. Further, our analyses clarified that consideration of only triple-phase boundary length is not enough to explain the overpotential dependence on microstructures. We therefore introduced a new index to relate overpotential characteristics with porous microstructures by taking into account both triple-phase boundary length and its spatial distribution.