ω-3 polyunsaturated fatty acids ω-3 PUFAs can help reduce symptoms of cachexia and reduce weight loss in patients with advanced malignant tumors. As an immune nutrient it can improve the perioperative immune function of patients with malignant tumors and reduce the levels of inflammatory markers improvement of the sensitivity and tolerance of treatment and reduce the therapeutic drug or radiation dose. The potential mechanisms of ω-3 PUFAs are ① increase the content of corresponding fatty acids in the phospholipids of the cell membrane involved in the inflammatory response thereby enhancing the fluidity of the cell membrane and reducing the activation of pro-inflammatory transcription factors such as nuclear factor-κB NF-κB specialized pro-resolving mediators SPMs including resolvins protectins and maresins regulating the inflammatory process. ② Eicosapentaenyl ethanolamide EPEA and DHEA derived from EPA and DHA were converted into EEQ-EA and EDP-EA isomers under the action of Cytochrome P450 CYP monooxygenases which inhibited the activation of JNK signaling pathway and alleviated the macrophage inflammatory response triggered by palmitic acid attenuating LTB4 - induced neutrophil mobility and activation. In addition EDPs inhibits angiogenesis induced by vascular endothelial generating factor VEGF and fibroblast growth factor 2 in vivo. ③ ω - 3 PUFA can selectively induce ferroptosis in cancer cells under environmental acidosis and produce toxic effects on tumor cells. Although ω- 3 PUFAs has been widely used in clinical practice its effects in the treatment and nutrition improvement of cancer patients are still inconsistent. More high-quality clinical trials and in-depth mechanism studies are needed.