Abstract: The assembly of collagen with natural organic molecules into crystalline structures offers promising avenues for the development of novel collagen-based biomaterials. However, the synthesis of such crystalline composite materials presents significant challenges due to the complexity of the underlying mechanisms, and systematic studies in this area remain scarce. In this study, we successfully constructed a crystalline material by employing a biomimetic mineralization strategy using the small-molecule polyphenol ellagic acid in conjunction with collagen. The mineralization process was governed by the concentration of collagen, commencing with the formation of hydrogen bonding between the phenolic hydroxyl groups of ellagic acid and the carboxyl groups of collagen, followed by self-assembly into its final morphology through hydrogen bonding and π-π interactions. The resulting material exhibited a cuboid-like morphology with length ranging from 20 to 30 micrometers. Characterization techniques, including laser confocal fluorescence microscopy, revealed a uniform distribution of collagen within the crystal. X-ray diffraction analysis confirmed that the material possesses a well-ordered lattice structure. Due to the stability of this crystal structure, the material maintains its structural integrity under various harsh conditions. This study provides novel methods and strategies for collagen self-assembly, offering valuable insights into collagen-based biomaterials.