Abstract: Because of the two major problems of electromagnetic compatibility and heat dissipation brought about by the development of 5G or 6G communication devices, supercomputers, wireless energy transmission devices, AI intelligence, quantum storage, VR technology, and microwave medical devices and other precision electronic devices toward miniaturization and high integration, it is essential to develop flexible wave-absorbing and heat-conducting composites with both good insulating properties, vibration damping, high efficiency wave-absorbing properties, and excellent heat-conducting capabilities. In this paper, from the design and preparation of single electromagnetic wave absorbing composites and heat dissipating composites, the electromagnetic wave absorbing mechanism and thermal conductivity mechanism as well as the important factors affecting the wave absorbing and thermal conductivity performance are summarized. On this basis, the comprehensive performance of some domes tic and foreign polymer-based wave-absorbing and heat-conducting composites and their design and preparation methods are introduced, and based on summarizing the current research status of existing wave-absorbing and heat-conducting multifunctional composites and the existing problems, and taking into consideration of the shortcomings in the current research and development of the current design, insights into the direction of the development of the polymer-based wave-absorbing and heat-conducting materials in the future are proposed. Through this study, we aim to provide a reference for the preparation of high-performance wave-absorbing and heat-conducting composite materials, improve the technical level of the industry, and develop new composite materials with both high thermal conductivity and excellent electromagnetic wave absorption ability.