Objective To observe the influence of U75302, blocker of leukotriene B4 receptor 1, on immune function in septic mice, so as to explore the implication of blocking leukotriene B4 receptor 1 for treatment of sepsis. Methods Experimental sepsis model was induced by cecal ligation and puncture (CLP). A total of 18 male C57BL/6 mice were randomly divided into sham group (n=6), CLP group (n=6) and CLP + U75302 intraperitoneal injection group (n=6). The peripheral blood cytokine tumor necrosis factor-α (TNF-α) and interleukin-10 (IL-10) levels, peritoneal lavage fluid Gr-1⁺ cell count and thymus T lymphocytes apoptosis were detected in mice of three groups 24 h after surgery. Results Compared with the CLP group, CLP + U75302 intraperitoneal injection group had significantly reduced blood TNF-α level (by 43%, P<0.05), significantly increased IL-10 level (by 88%, P<0.05), signficantly decreased Gr-1⁺ cell counts in peritoneal lavage fluid (P<0.05), and significantly decreased apoptosis of thymus T lymphocytes (P<0.01). Conclusion Blocking leukotriene B4 receptor 1 with U75302 may decrease peripheral TNF-α level, increase IL-10 level, and improve cellular immunity, which may be involved in inflammation of sepsis.