Abstract: OBJECTIVE To explore the etiological characteristics of postoperative pulmonary infections in the patients undergoing emergency craniotomy and observe the expressions of serum inflammatory factors and Toll-like receptor 4 (TLR4) /nuclear factor-κB (NF-κB) signaling pathways. METHODS A total of 284 patients who underwent emergency craniotomy in Zhoukou Vocational and Technical College from Jun 2019 to Sep 2022 were enrolled in the study and were divided into the infection group with 47 cases and the non-infection group according to the status of postoperative pulmonary infection. The clinical specimens were collected from the patients with infection, pathogens were cultured, and the expression levels of TLR4/NF-κB signaling pathway inflammatory factors were observed and compared between the two groups of patients. RESULTS Of the 284 patients who underwent the emergency craniotomy, 47 were complicated with postoperative pulmonary infection, with the incidence of pulmonary infection 16.55%. Totally 55 strains of pathogens were isolated, 40 (72.73%) of which were gram-negative bacteria, 10 (18.18%) were gram-positive bacteria, and 5 (9.09%) were fungi. The relative expression levels of serum soluble triggering receptor expresses on myeloid cells-1(sTREM-1), procalcitonin (PCT), C-reactive protein (CRP)/albumin (ALB), interleukin-4 (IL-4), TLR4 and NF-κB mRNA of the infection group were higher than those of the non-infection, and the expression levels of serum TLR4 and NF-κB proteins of the infection group were higher than those of the non-infection group(P＜0.05). Among the 284 patients who underwent the emergency craniotomy, 28 died, with the mortality rate 9.86%. The relative expression levels of serum sTREM-1, PCT, CRP/ALB, IL-4, TLR4 and NF-κB mRNA of the death group were higher than those of the survival group, and the expression levels of serum TLR4 and NF-κB proteins of the death group were higher than those of the survival group (P＜0.05). CONCLUSION The gram-negative bacteria are dominant among the pathogens isolated from the emergency craniotomy patients with postoperative pulmonary infection, the patients are complicated with the changes of TLR4/NF-κB signaling pathways and inflammatory factors, which is closely associated with the prognosis and may serve as the new targets for clinical diagnosis and treatment.