【Abstract】 Objective To investigate the effect and mechanism of cyclosporine A on the occurrence of pulmonary fibrosis in paraquat poisoning. Methods 60 adult male SpragueDawley (SD) rats were randomly divided into normal group (n=12), PQ group (n=30), CsA high, medium and low dose group (n=18). PQ group rats were divided into four time points: 1 day, 3 days, 7 days and 14 days. Each time point included 6 rats. 20% PQ solution (50 mg/kg) were selected for once administration gavage . Choose the time point of autophagy occurred evidently as CsA intervention time point. Each CsA group was administration gavage CsA with dose 5 mg/(kg·day), 10 mg/(kg·day) and 15mg/(kg·day) before gavage PQ. The change of lung tissue pathological lesion, lung tissue′s mitochondrial transmembrane potential (MMP), PINK1 and Parkin were measured.Results Compared with that of normal group, the degrees of pulmonary fibrosis, the PINK1 and Parkin of PQ groups were gradually increased and the red/ green fluorescence ratio of PQ groups was decreased (P＜001). The degrees of pulmonary fibrosis, the PINK1 and Parkin of CsA groups were lower than that of PQ groups (P＜005). The red/ green fluorescence ratio of CsA groups was higher than that of PQ groups (P＜005). ConclusionCyclosporine A can reduce PINK1 / Parkin protein, mitigate the mitochondrial autophagy caused by paraquat poisoning and improve pulmonary fibrosis.