|Abstract:A conical millimeter wave dielectric probe for the auxiliary diagnosis of skin cancer was studied. The probe operates at 35 GHz and consists of a metal circular wave-guide and a tapered PTFE dielectric probe. Millimeter wave reflectometry（ S11 parameters） are potential diagnostic tools capable of distinguishing between healthy and malignant skin tissue. Based on the Pennes heat transfer equation, a skin heat transfer model was established to study the effects of millimeter wave input power, irradiation time and blood perfusion rate on skin temperature. When the skin was continuously irradiated for 10 minutes with an input power of less than 300 mW, the skin temperature around the probe was always below 40 within a safe temperature range. When the input power was between 300mW and 600mW, the temperature around the probe will exceed the skin pain threshold temperature, According to the Arrhenius injury model, when the input power was 900mW, the tumor tissue with a radius of 6.5 mm around the probe will be in completely irreversible damage state.