In the measurement of the permittivity of biological materials,it is universal todeal with the layered structure of biological tissues,such as skin and hypoderm.Ananalytical expression of the equivalent circuit of an open—ended coaxial probe con-nected with bilayered dielectrics,ε_1 and ε_2,has been found by means of the confor-mal transformation method,which can be expressed as three parallel capacitancesC_f,Coε_1 and C_1 (ε_2—ε_1).Where C1 is the additional capacitance of the probe for bi- In the measurement of the permittivity of biological materials, it is universal to deal with the layered structure of biological tissues, such as the skin and hypoderm. Ananalytical expression of the equivalent circuit of an open-ended coaxial probe con-nected with bilayered dielectrics, ε_2, has been found by means of the confor-mal transformation method, which can be expressed as three parallel capacitances C_f, Coε_1 and C_1 (ε_2-ε_1) .here C1 is the additional capacitance of the probe for bi-