A　simulation-experiment　method　is　proposed　to　characterize　the　performance　of　a　realistic　microwave　ablation　(MWA)　device.　Ex-vivo　porcine　livers　are　used　in　the　study.　The　catheter　is　modeled　without　understanding　its　electrical　structure　or　the　actual　ablation　power;　so,　it　is　adaptable　to　other　ablators.　The　optimized　3-D　finite　difference　time　domain　(FDTD)　simulation　can　efficiently　reflect　the　lesion　profile　in　heterogeneous　tissues　and　is　clinically　beneficial.　This　method　can　serve　as　a　guideline　to　evaluate　the　device　performance　and　the　treatment　plan.　The　influence　of　the　temperature　dispersive　dielectric　and　the　thermal　properties　has　also　been　discussed.