Abstract: Objective To observe the effect of high-dose ambroxol combined with acetylcysteine on pulmonary fibrosis in patients with paraquat poisoning. Methods A retrospective analysis was made on 90 patients with paraquat poisoning treated in the Third People's Hospital of Wuxi City from May, 2016 to May, 2017. The patients were randomly divided into control group by random number table method (using Dan red injection) and observation group (large dose ammonia bromine joint acetylcysteine group). General information of the two groups were comparable. All patients were given symptomatic support treatment, prevent related complications, such as a sedative and analgesic, oral care, etc. At the same time, large doses of ambroxol were added to all patients on the basis of methylprednisolone treatment, and acetylcysteine effervescent tablets were administered to the observation group on the basis of the control group. The respiratory function of the patients was closely observed, and the renal function, urine and feces of the patients were monitored. Survival rate, incidence of pulmonary fibrosis and degree of pulmonary fibrosis were observed. Results According to the analysis of patients' inpatient registration, the difference in survival rate between the observation group and the control group at the same time point was not statistically significant (P>0.05), and the difference in incidence of pulmonary fibrosis between the two groups at the same time point was not statistically significant (P>0.05). The degree of pulmonary fibrosis in the observation group was significantly lower than that in the control group,and the difference was statistically significant (P<0.05). Conclusion Comparing with Danhong injection alone, the survival rate is not significantly improved in the group of high-dose ambroxol combined with acetylcysteine in the early clinical treatment of paraquat-induced pulmonary fibrosis patients, the incidence of pulmonary fibrosis is not significantly reduced.However, the degree of clinical symptoms can be improved. It is worthy to be promoted due to high safety and efficacy.