This work presents a new method, and its instrument, to measure the thermal conductivity of materials. It employs two different materials, so it is a differential instrument. In this proposed method a thermal wave is generated on one of the surfaces of a given sample, and the temperature is measured at the other surface. From the relationship between the input and output waves is possible to obtain the thermal conductivity of one material. The equation of heat conduction, which describes the behavior of the system, on the materials was deduced and simulated, allowing to determine the temperature at any point of the materials. Along with the equations, the Network Simulation Method was applied to solve the problem, but with a different approach. The experimental setup uses thermoecletric coolers to control temperature, and T thermocouples to measure the temperature. The materials used to apply the method were both thermal insulating and conductive, and with few millimeters thick. Several experiments were performed in order to validate the method and they indicate the feasibility of the instrument.Nomenclature: α -Thermal diffusivity (m 2 /s) κ -Thermal conductivity (W/(mK)) ρ -Density (kg/m 3 ) C p -Specific heat capacity (J/(kgK)) h -Heat Transfer Coefficient H -Sample thickness (mm) L -Total thickness (mm) β -Material parameter ( iω α ) ω -Angular frequency (rad/s)) κ -thermal conductivity (W/(mK)) R -Both sample and reference radius (mm)