Abstract: Thermal interface materials could effectively transfer the heat from electronic devices with high temperature to the thermal management components, so as to alleviate the problems of deterioration of component life caused by overheating of electronic devices. In recent years, the polymer-based composites composed of polymer matrix and reinforcing fillers with high thermal conductivities have been widely concerned because of their low density and adjustable thermal conductivities. Different from the conventional composites with randomly dispersed fillers, the construction of three-dimensional (3D) continuous network structure in the polymer matrix could significantly increase the filler/filler contact, reduce the percolation threshold of thermal conductivity and the interfacial thermal resistance, and then significantly improve the thermal conductivities of composites. Firstly, the thermal conductivity mechanisms of polymer-based thermal conductive composites were briefly analyzed. Secondly, the construction processes of polymer-based thermally conductive composites with interconnected network structures were summarized, mainly including the pre-construction of 3D thermally conductive filler network, the post-processing based on polymer particle/powder, the post-processing based on polymer fiber/fabric, and the film casting or flocculation based on polymer latex. The effects of different types of thermal conductive fillers on the thermal conductivities of polymer composites were summarized, mainly including metal fillers, ceramic fillers, carbon-based fillers and their hybrid fillers. Finally, the development prospects of polymer-based thermally conductive composites with interconnected network structures were prospected.