Abstract: DHA or docosahexaenoic acid is one of marine polyunsaturated fatty acids. It was close relation with our body health, and it has many physiological function. It is indispensable to healthy growth of infants and young children in the process of nutritional factors, as well as the prevention and treatment of cardiovascular disease and cancer also has very good efficacy. DHA can inhibit cell proliferation, metastasis, inhibiting intracellular signal transduction pathways, inducing differentiation and apoptosis, improving the patient's physique, improve survival rates, exert inhibitory effect on a variety of cancer cells. n-3 PUFAs have a variety of biological functions of nutrients, which regulate the body's immune function and have been more and more attention. The inhibition cancer functions of DHA was reviewed in this paper, and the controling class arachidic acid biosynthesis and regulation of signaling pathways were mainly recommended, influence of transcription factors and gene expression and enhance the lipid peroxidation were also discussed.