Objective To systematically evaluate the efficacy of ω⁃3 polyunsaturated fatty acids in radiotherapy and to provide evidence⁃based reference for its use in radiotherapy. Methods Randomized controlled trials (RCT), which utilized the regular diet or standard enteral nutrition preparations (control group) and combined with ω⁃3 polyunsaturated fatty acids (experimental group) to improve the nutritional status in patients during radiation therapy and prevent of complications were collected from PubMed, Medline, Embase, the Cochrane library, China journal full⁃text database and Wanfang database, until to May 2020. Data of clinical trials that met the inclusion criteria were extracted and quality evaluation of the trials was conducted with reference to Cochrane systematic evaluator′s manual 5.1. The Stata 14.0 statistical software was used to meta⁃analyze the weight loss before and after radiotherapy and the incidence of complications of severe anorexia, vomiting and diarrhea in the two groups. Results a total of 10 RCTs were included, with 486 patients. The results of meta⁃analysis showed that no statistically significant difference between two groups was found on weight loss（SMD＝-0.02，95%CI：-0.26-0.21，P＝0.838）, decreased BMI value（SMD＝0.06，95%CI：-0.23-0.34，P＝0.696）, the incidence of overalladverseevents（RR=0.97，95%CI：0.84-1.12，P＝0.678）, and the incidence of anorexia（RR＝0.79，95%CI： -0.49-1.28，P＝0.345）after radiotherapy. Conclusion The combination of ω⁃3 polyunsaturated fatty acids with normal diet or routine nutritional preparations did not restore weight loss and prevent adverse events in patients undergoing radiotherapy.