Docosahexaenoic acid (DHA) is an important omega-3 long-chain polyunsaturated fatty acid. As a main fatty acid in the brain and retina, DHA is crucial for the neurological health of fetuses, infants, and the elderly. It can help to improve cardiovascular health, prevents cognitive decline, and has anti-inflammatory and antioxidant effects. The structure, functions, and main sources of DHA were reviewed, with a focus on the challenges faced by microbial DHA oil synthesis, particularly the complexity of metabolic pathways and the diversity of oil components. The strategies for enhancing DHA production were also discussed, including the directional selection of lipid-producing microorganisms, regulation of metabolic mechanisms, and the application of fermentation amplification technology. Furthermore, the future development of DHA-rich oil derivatives has been prospected, highlighting products with greater potential. With continuous advancements in biotechnology and metabolic engineering technology, the applications of DHA-rich oils would extend beyond traditional dietary supplements to encompass functional foods, precision nutrition, and medical therapeutics, and ect., promoting the development of DHA products toward higher value-added applications with enhanced bioactivity.