Objective:To explore the effect of piperacillin sodium and tazobactam sodium for injection combined with ambroxol hydrochloride on sputum characteristics,pulmonary inflammation,and respiratory mechanics in patients with severe pneumonia(SP).Methods:A total of 106 patients with SP were divided into the control group and the observation group according to different treatment methods,with 53 cases in each group.On the conventional treatment basis,the control group was treated with piperacillin sodium and tazobactam sodium for injection,and the observation group was treated with ambroxol hydrochloride on the basis of the treatment of con-trol group.After 14 d of treatment,the two groups were compared on clinical efficacy,clinical indicators,sputum characteristic scores,inflammatory indicators,and respiratory mechanics indicators.The occurrence of adverse reactions was recorded.Results:After 14 d of treatment,the total effective rate,bacterial clearance rate,sputum volume score,and dynamic lung compliance of the observation group were higher compared with the control group(P＜0.05).The duration of fever,duration of mechanical ventilation,sputum change time,cough and sputum characteristic scores,C-reactive protein,tumor necrosis factor,procalcitonin,work of breathing and peak airway pres-sure were lower than those of the control group(P＜0.05).The incidence rates of adverse reactions in the two groups during treatment were 7.55%and 11.32%,with no significant difference(P>0.05).Conclusion:Piperacillin sodium and tazobactam sodium for in-jection combined with ambroxol hydrochloride is effective in the treatment of SP,which can effectively improve sputum characteristics and respiratory mechanics,and alleviate pulmonary inflammation,with good safety.