Abstract:To observe the effect of ulinastatin combined with large dose ambroxol on pulmonary function and oxidative stress in patients with severe burn. Methods 106 cases severe burned patients were randomly divided into the observation group (55 cases) and the control group (51 cases). The observation group was given ulinastatin and large dose ambroxol (Namely: 210 mg/t, one time every 8 hour intravenous infusion) based on conventional therapy, and the control group was given ulinastatin and routine dose ambroxol(Namely: 30 mg/t, one time every 8 hour intravenous infusion) based on conventional therapy. After 10-days treatment, the differences of pulmonary function indexes (FVC, FEV1, PEF, PEF 25% and PaO2, PaCO2, PaO2/FiO2) and oxidative stress indexes (MDA, MPO, LPO, TAO) were observed between two groups. Results The results of FVC, FEV1, PEF and PEF25 in two groups were compared, a: the FVC, FEV1, PEF, PEF25 levels were difference (F group = 3.103, 4.224, 3.184 and 3.827,p < 0.05) at different time points; b: all indexes of the two groups were difference (F time = 4.430, 5.037, 4.472 and 4.014,p < 0.05). and the observation group were higher than those of the control group, had better lung function. c: the variation tendencies of FVC, FEV1, PEF and PEF25 levels in the two groups were different (F interaction = 3.015, 3.472, 3.204 and 3.811,p < 0.05).The results of PaO2, PaCO2, PaO2/FiO2 in two groups were compared, a: the PaO2, PaCO2, PaO2/FiO2 levelswere different ( Fgroup = 6.338, 8.03 and 9.238, p< 0.05) at different time points; b: all indexes of the two groups were different (F time = 8.429, 7.038, 6.256,p = 0.000). and the observation group were better than those of the control group, had better blood gas indexes; c: the variation tendencies of p< 0.05) levels in the two groups were different (F interaction = 5.104, 5.472 and 4.629, p= 0.000). The results of MDA, MPO, LPO, TAO in two groups were compared, a: the MDA, MPO, LPO, TAO levels were different (F group = 5.356, 6.230, 8.375,11.025,p = 0.000) at different time points; b: all indexes of the two groups were different (F time = 8.273, 8.429,10.632 and 9.172,p = 0.000). and the observation group were lower than those of the control group, had lower oxidative stress; c: The variation tendencies of MDA, MPO, LPO, TAO levels in the two groups were different(F interaction = 4.917, 6.335, 6.274 and 5.923, p= 0.000). Conclusions Ulinastatin combined with large dose ambroxol can improve the pulmonary function and inhibit oxidative stress reaction significantly.