The effective electric conductivity of metal-polymer composite is investigated theoretically as a function of the electric conductivities of the constituents, of the particle shape and size and of the volume of loading. And, in order to consider the interaction between the metal particles, a self-consistent way is used to improve this function. Firstly, the percolation threshold decreases rapidly with increasing the metal particles axial ratio and decreasing the metal particle size. Secondly, the dependence of the metal particle shape and size on the effective electric conductivity of metal-polymer composite is investigated. Finally, the theoretical results on the effective electric conductivity of tin-polypropylene composite are in good agreement with the experimental data. (C) 2003 Elsevier Ltd. All rights reserved.