Abstract: 【Objective】 The purpose of this study was to investigate the effects of triclocarban (TCC) on immune function and the expression of Toll-like receptor 4 (TLR4)/myeloid differentiation factor 88 (MyD88)/nuclear factor κB (NF-κB) signaling pathway in spleen of rats.【Method】 A total of 96 5-week-old male SD rats were randomly divided into 4 groups： Corn oil control group (group C) and 0.1，20 and 100 mg/kg TCC groups (TL，TM and TH)，with 24 rats in each group. Different doses of TCC were thoroughly mixed with corn oil and given intragastric administration once a day. Rats in group C were given intragastric administration of the same amount of corn oil without TCC，the experiment lasted for 60 days. After the experiment，blood and spleen tissues of rats were collected，and serum biochemical indexes，splenic lymphocyte proliferation capacity，macrophage phagocytosis index，serum hemolysin level and spleen natural killer cell (NK) activity were detected. The serum immunoglobulin content of rats was detected by ELISA. The lymphocyte subsets in peripheral blood of rats were detected by flow cytometry. Real-time quantitative PCR and Western blotting were used to detect mRNA and protein expression levels of TLR4/MyD88/NF-κB pathway marker genes and downstream factors，respectively.【Result】 Compared with group C，serum glucose (Glu) level in TH group was significantly decreased (P＜0.05), and serum creatinine (CREA) level in TM group was significantly increased (P＜0.05). The splenic lymphocyte proliferation ability and serum hemolysin level of TM group were significantly decreased (P＜0.05). ELISA results showed that the levels of immunoglobulin A (IgA)，IgM and IgG in serum of rats in TH group and IgG in serum in TM group were extremely significantly decreased compared with group C (P＜0.01). Flow cytometry results showed that，compared with group C ，there were no significant differences in the proportion of CD3⁺，CD4⁺ T cells and the ratio of CD4⁺ and CD8⁺ in peripheral blood of rats in different doses of TCC groups (P ＞ 0.05). Real-time quantitative PCR results showed that，compared with group C，the mRNA relative expression levels of TLR4，MyD88 and IL-1β in spleen of rats in different doses of TCC groups were significantly or extremely significantly increased (P ＜ 0.05 or P ＜ 0.01). Western blotting results showed that compared with group C，the expressions of TLR4，MyD88 and NF-κB proteins in spleen of TM group were extremely significantly increased (P ＜ 0.01).【Conclusion】 TCC could produce certain toxic effects on cellular and humoral immunity of rats，and significantly activate the TLR4/MyD88/NF-κB signaling pathway in rat spleen. TCC might damage the immune system of rats by targeting the TLR4/MyD88/NF-κB pathway in the spleen and induce immunotoxicity in rats.