To investigate the role of found in inflammatory zone 1 (FIZZ1) protein in the pathogenesis of experimental pulmonary fibrosis, 48 male Sprague-Dawley rats were randomly divided into two groups, the pulmonary fibrosis group and the control group. Rat pulmonary fibrosis was reproduced by an intratracheal injection of bleomycin (5 mg/kg body weight). Normal saline (1 ml/kg body weight) was given intratracheally injection in the control group. There were 24 rats in each group, and 6 animals were separately killed on the 7th, 14th, 21th and 28th day after treated with bleomycin or normal saline. Then the following tests were undertaken: (1) HE and Masson staining of lung section;(2) Determination of lung tissue hydroxyproline (HYP);(3) Immunohistochemical staining of protein of FIZZ1 in the lung;(4) In situ hybridization of FIZZ1 mRNA in the lung. The results showed: (1) There were full of inflammatory cells in the lung, the interval of alveoli enlarged and many alveolar spaces disappeared on the 7th day after treated with bleomycin in the fibrosis group. Collagen began to proliferate after 14 d. The pulmonary fibrosis was stably established on the 28th day, full of green fibers in the Masson staining of lung section. (2) The expression of FIZZ1 protein in the lung increased after 7 d in bleomycin-treated animals (3.013+/-0.326 vs 0.473+/-0.056, P<0.01 vs control), but was slightly decreased on the 14th day (2.124+/-0.197) and expensively decreased on the 21st day (1.760+/-0.105) and the 28th day (0.691+/-0.081). (3) The expression of FIZZ1 mRNA in the lung also increased after 7 d by treated with bleomycin (3.795+/-0.338 vs 0.678+/-0.087, P<0.01 vs control), but decreased on the 14th day (1.276+/-0.104) and further decreased on the 28th day (0.896+/-0.084). The expression of FIZZ1 protein and mRNA in fibrosis group was higher than that in the control group (P<0.05 or P<0.01). The results suggest that FIZZ1 protein and FIZZ1 mRNA are dynamically changed in the lung with experimental pulmonary fibrosis, which may contribute to the pathogenesis of pulmonary fibrosis.