Objective To study the effect of taurine on the humanized nude mouse model of triple-negative breast cancer. Methods Five-week-old SPF level nude mice（n=10） were inoculated with MDA-MB-231 breast cancer cells and randomly divided into one group that received normal drinking water and another group that received water containing 5% taurine（n=5 animals per group）. Tumor volume and weight were examined after treatment, and Western blotting was used to assess expression of estrogen receptor （ER）, progesterone receptor（PR），human epidermal growth factor receptor 2 （HER-2）and guanosine triphosphatase-activating protein p21ras. Results All mice survived until the end of the experiment，and all tumors grew. Compared to control mice, mice given taurine had tumors with 41.6% smaller weight and volume（P<0.05），134% higher expression of ER（P<0.05）, 47.5% higher expression of PR （P<0.05），67% lower expression of HER-2（P<0.05）and 62.2% lower expression of p21ras（P<0.01）. Conclusion Taurine inhibits tumor growth by up-regulating expression of ER and PR and down-regulating expression of HER-2 and p21ras.