Abstract: OBJECTIVE To explore the curative effect of ulinastatin on acute lung injury after severe traumatic brain injury. METHODS One hundred patients with acute lung injury after severe traumatic brain injury were randomLy divided into control group and treatment group with fifty patients in each group. Control group obtained common treatment and treatment group obtained common treatment plus ulinastatin. The concentration of plasma interleukin-6(IL-6), C-reactive protein(CRP), tumor necrosis factor-α(TNF-α), S100B protein, neuron specific enolase(NSE), glial fibrillary acidic protein(GFAP), myelin basic protein(MBP), surfactant protein D(SP-D), and Clara cell protein was measured by ELISA before treatment and ten days after treatment. Glasgow outcome scale(GCS) scores were investigated three months after treatment. RESULTS Before treatment, the concentration of plasma IL-6, CRP, TNF-α, NSE, GFAP, MBP, SP-D, S100B protein, and Clara cell protein in control group and treatment group was compared, and there was no significant difference. After treatment, the above concentration was obviously lower than before treatment in both control group and treatment group. After treatment, the concentration of plasma IL-6, CRP, TNF-α, NSE, GFAP, MBP, SP-D, S100B protein, and Clara cell protein in treatment group was significantly lower than in control group. Three months after treatment, GCS scores suggested that 5 patients had good recovery, 7 patients had moderate disability, 11 patients had severe disability, 7 patients kept persistent vegetative state and 16 patients died in the control group. Thirteen patients had good recovery, 14 patients had moderate disability, 6 patients had severe disability, 8 patients kept persistent vegetative state and nigh patients died in the treatment group. The prognosis was obviously better in treatment group than in control group. CONCLUSION Ulinastatin exerts obviously curative effect on acute lung injury after severe traumatic brain injury. Its mechanism may be related to the improvement of brain and pulmonary injury by inhibiting the inflammatory response.