Lightweight composite sandwich structures consist of thin and strong panels and lightweight porous cores, and diversity of their core structures drives the development of sandwich structures. In nature, various types of organisms have formed the most suitable biological structure for their survival and reproduction during the long-term evolution process, in which the high-strength structure has inspired researchers to carry out biomimetic design of sandwich structure cores. In this paper, research status of biomimetic core structure of water animals, land animals, flying animals, as well as plant fruits, roots, stems, and leaf veins is reviewed, and design concepts of biomimetic composite sandwich structure cores and topologies are described. The improvement of mechanical properties of bionic composite sandwich structure and its application in related engineering are introduced. Finally, based on the current development status of bionic composite sandwich structures, scientific challenges are presented and outlook is given.