Deoxyribonucleic acid (DNA), as a natural polymer material, carries almost all the genetic information and is recognized as one of the most intelligent natural polymers. In the past 20 years, there have been many exciting advances in the synthesis of hydrogels using DNA as the main backbone or cross-linking agent. Different methods, such as physical entanglement and chemical cross-linking, have been developed to perform the gelation of DNA hydrogels. The good designability, biocompatibility, designable responsiveness, biodegradability and mechanical strength provided by DNA building blocks facilitate the application of DNA hydrogels in cytoscaffolds, drug delivery systems, immunotherapeutic carriers, biosensors and nanozyme-protected scaffolds. This review provides an overview of the main classification and synthesis methods of DNA hydrogels and highlights the application of DNA hydrogel in biomedical fields. It aims to give readers a better understanding of DNA hydrogels and development trends.