Abstract: With the rapid development of electronic devices toward high integration, high power density, and miniaturization, the power density of devices continues to increase, creating an urgent demand for efficient and reliable thermal management materials. Polyimide (PI), known as the “golden plastic” due to its outstanding thermal stability, electrical insulation, mechanical properties, and excellent processability, exhibits significant potential for applications in electronic packaging and flexible devices. However, limited by the randomly disordered structure of its molecular chains, PI possesses intrinsically low thermal conductivity, which makes it difficult to meet the heat dissipation requirements under high heat flux conditions. Therefore, systematic research on strategies for enhancing the thermal conductivity of PI is of great significance. Based on the heat transfer mechanisms of polymers and their composites, this paper systematically reviews recent key strategies for improving the thermal conductivity of PI, including the regulation of molecular chain structures and liquid-crystalline structures to enhance intrinsic thermal transport, interface engineering and heterogeneous filler hybrid design to reduce interfacial thermal resistance, as well as multiscale structural regulation methods such as layered architectures, template-induced construction, and external physical-field-assisted orientation. By summarizing the influence of different structural design strategies on the construction of thermal conduction networks, the structure–property relationships of high-thermal-conductivity PI materials are clarified, and the future development directions of high-thermal-conductivity PI-based composites are also discussed.