<p>Polymer film-based dielectric capacitors are required to operate stably and efficiently at extreme temperatures in the emerging applications including underground oil and gas extraction, electrified transportation and space exploration, etc. However, the commercial benchmark polymeric dielectric, biaxially oriented polypropylene, can only withstand up to 105 °C, and its electrical insulation performance deteriorates sharply with increasing temperature. Recently, numerous reported strategies, such as surface engineering of polymer films and polymer-inorganic particle blending have reached considerable achievements in balancing the temperature capability and electrical insulation properties of polymeric dielectrics, but show less promise in production scale-up with respect to the all-organic dielectric systems. In this review, we summarize the recent progress of polymer molecular structure design and all-organic composite systems towards high-temperature capacitive energy storage. The correlation of high-temperature capacitive energy storage performance and multi-level structures of all-organic dielectrics is established, and the effect of molecular structures on the charge transport behavior is analyzed. Moreover, the strategy of utilizing materials informatics to design the molecular structure of high-temperature polymers is introduced. Finally, the advantages and limitations of all-organic polymer dielectrics in the field of high-temperature capacitive energy storage are summarized, and the future development directions are highlighted.</p>