Ulcerative colitis is a chronic non-specific inflammatory disease of the colon and rectum and is a type of inflammatory bowel disease (IBD). The aim of this paper was to investigate the effect of Haematococcus carbon dots (HP-CDs) on dextran sulfate sodium (DSS)-induced ulcerative colitis in mice. HP-CDs were prepared from Haematococcus (HP) powder, firstly by hydrothermal synthesis of Rhodococcus amphitrite. The effect of HP-CDs on the mouse model of DSSinduced ulcerative colitis was then investigated in terms of histology and pathology. Effects. The results showed that HP-CDs significantly attenuated colitis and reduced body weight loss, Disease Activity Index score and colonic atrophy. In addition, HP-CDs reduced MPO activity and the expression of pro-inflammatory cytokines, such as TNF-?, IL-1?, and IL-6, in colonic tissues.