The results of investigations of electrical conductivity of polymer composites based on epoxy resin with different types of nanocarbon filler under thermal load have been investigated. Nanocarbon materials with different structure and shape of particles (different aspect ratio) have been used as fillers in the preparation of polymer composites. A study of the temperature dependence of the electrical resistance of polymer composites with a content of up to 10% of different types of nanocarbon fillers in the temperature range from 77 to 293 K has been carried out. It is shown that that the temperature dependence of the electrical conductivity of polymer composites with nanocarbon fillers is formed as a result of the interaction of several factors among them the conductivity of the nanocarbon filler itself, the shape (aspect ratio) of the nanocarbon filler particles and the structural and morphological state of its surface and also the ratio between the values of coefficients of thermal expansion for the polymer matrix and nanocarbon filler particles. It has been revealed that for nanocarbon filler particles with large aspect ratio the effect of thermal expansion of the polymer on the contact resistance between the filler particles is levelled off, while for nanocarbon fillers with a small aspect ratio value the difference between the CLTE values has the main effect on the contact resistance.