Abstract: To discuss the immune mechanism of infectious bovine rhinotracheitis virus （IBRV） after infecting on bovine monocyte macrophages, bovine peripheral blood mononuclear cells were isolated by Ficoll-Hypaque density gradient centrifugation and monocyte macrophages were obtained by adherent culture. The content of nitric oxide （NO）secreted by bovine monocyte macrophages was detected by Griess method after IBRV was infected 6, 12, 24 and 48 hours. The results showed that the content of nitric oxide （NO） secreted by bovine monocyte macrophages after IBRV was injected was higher than that of control group （P〈 0.05） and the amount of nitric oxide produced by macrophages reached the highest level （607.87μmol/L）after 24 hours. IBRV infection could affect the amount of nitric oxide secreted .by monocyte macrophages,which might be related to pathogenesis caused by IBRV.