Abstract: Aiming at the defects of poor conformability, carbonization and electromagnetic radiation of the current traditional minimally invasive thermal ablation technology, this paper proposes a steam thermal ablation technology that uses saturated steam internal energy to replace the traditional electromagnetic radiation energy. Through the steam thermal ablation system and the steam ablation needle designed based on simulation, the ex vivo pig liver experiment was carried out. The results have the characteristics of the maximum ablation axis ratio (short diameter / long diameter) and no carbonization in the same type of thermal ablation technology. Based on the near-infrared light, the curative effect of the reduced scattering coefficient of the steam ablation results was evaluated. The reduced scattering coefficient of the coagulation area was more than 16, reaching the completely damaged state, which verified that the steam ablation can completely inactivate the tumor cells.