A series of the thermal conductive polyamide 66 (PA66) composites were prepared by two methods, including extrusion method (EM) and solution method (SM). The thermal conductivity, mechanical properties, thermal stability, and electric property of PA66 composites were investigated. The results showed that the maximum value of thermal conductivity of carbon fiber/PA66 composites containing 40 wt% carbon fiber prepared by SM achieves 2.537 W/m·K, which was superior to that of carbon fiber/PA66 composites prepared by EM at the same carbon fiber content. Moreover, its value was eight times more than that of pure PA66. The orientation of carbon fiber in process of injection had an influence on thermal conductivity of carbon fiber/PA66 composites, and the perpendicular distribution of carbon fibers helped in improving the thermal conductivity of composites. The carbon fiber/PA66 composites had good heat conducting performance but also had good material properties and electrical properties.