The electronic transport and magnetic properties of nanocomposites, in which nanoparticles of superconducting (SC) molybdenum carbides are embedded in a ferromagnetic (FM) carbon matrix to form a three-dimensional SC-FM network, are studied. The high-resolution transmission electron microscope observation shows that the carbon in the nanocomposites is in both ordered and disordered forms. The magnetic properties of the nanocomposites are ruled by the ferromagnetic carbon matrix. The temperature dependence of electrical resistivity of the nanocomposites is dominated by the carbon matrix, showing the semi-conductivity. The special I-V curves near the zero voltage bias of the nanocomposites are observed at low temperatures, due to the influence of contact barriers between molybdenum carbides and the carbon matrix.