Objective To investigate the effect of CD226 knockout (KO) on radiation-induced liver injury in mice. Methods Wild-type (WT) and CD226KO mice were randomly divided into naive group and irradiated group. The mice in the irradiated group were exposed to an 8 Gy of 60Co γ-radiation. The survival rate was observed and body mass loss was measured. The pathological changes in the liver and colon were examined by HE staining, and the mRNA levels of inflammatory factors, including inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), IL-6, IL-12p40, tumor necrosis factor α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) were detected by real-time quantitative PCR. Results Compared with the irradiated WT mice, the irradiated CD226KO mice had increased body mass loss and decreased survival rate. In the irradiated CD226KO mice, the liver injury was more serious, the liver index (liver mass/body mass) was reduced, and the expressive levels of iNOS, IL-1β, IL-6, IL-12p40, TNF-α and MCP-1 were enhanced; whereas, the colitis was less serious, and the expressive levels of inflammatory factors were down-regulated. Conclusion The deficiency of CD226 can decrease the survival rate of irradiated mice, which is associated with the aggravated liver injury.