The use of nanocomposite materials has led to progress in the creation of new electronic devices (minitransistors, sensors, micro-drives, which are used to build artificial muscles, and supercapacitors. Nanocomposites occupy a special place with magnetosensitive fillers, particularly successfully used in medicine. Nanocomposites are also used for a protective coating. Depending on the operational functions, achieving a specific conductivity value and its change with temperature is necessary for such a coating. In the work, a conductivity model of polymer nanocomposites based on graphene (Gr/PS) was obtained using experimental data. The largest relative deviation between the conductivity surface and experimental data does not exceed 9.5%. The expression was obtained for the graphene concentration 1 < C(Gr) < 30 wt % and the temperature range 20 < T < 100 °C. The dependence of the specific electrical conductivity on the filler concentration and temperature obtained in the work will allow the researchers to select a nanocomposite with the required conductivity and evaluate the temperature effects on it for the conditions to which the material will be exposed.