Polyethylene(PE)/boron nitride (BN)/ devulcanized waste rubber powder (WRP) composites were prepared by melt blending and compression molding. In the blending, the three- dimensional network structure of WRP can maintain its initial structure during mechanical processing. BN platelets disperse in the PE matrix to form thermally conductive segregated network, which improves the thermal conductivity of the composites. When the BN mass fraction is 30% and mass ratio of PE to WRP is 1/2, the thermal conductivity of the PE/BN/WRP composite is 1.73 W/(m × K). Compared with the PE/BN composite, the thermal conductivity of the PE/BN/WRP composite is increased by 37.3%, which is 4.33 times that of pure PE. The impact strength is 8.3 kJ/m², which is 55.4% higher than that of the PE/BN composite. This study used devulcanized WRP to prepare the high thermally conductive composite, which provides a new idea for the high-value and functional utilization of waste vulcanized rubber.