The case is a 74-year-old-female who was treated with percutaneous transhepatic low output microwave tissue coagulation therapy (PLMCT) using a new needle electrode 1 mm in diameter for liver tumor. This needle electrode is more useful than an old type 16 G needle electrode in strength and for the point that coagulated tissue is hard to adherent to the electrode. PLMCT was performed at the output of 30 watt for 90 seconds at a time. Tumor 1.5 cm in diameter was completely coagulated by irradiation 6 times and blood flow of vessel in touch with tumor was preserved judged by enhanced CT. The results suggested that PLMCT using a new electrode 1 mm in diameter is a useful therapy for small solitary liver tumor.