Inclusion Criteria:

1. Written informed consent signed;

2. 18-75 years of age;

3. Clinically or multidisciplinarily diagnosed idiopathic pulmonary fibrosis(see 2011
guidance );

4. Resting state PaO2≥50mg, FVC%≥45% normal predicted value and DLCO≥30% normal
predicted value.

Exclusion Criteria:

1. Allergic to pirfenidone;

2. Dyspnea symptoms relieved in the past 6 months;

3. Patients in acute exacerbation phase;

4. Diabetic patients whose fasting venous glucose >11.1 mmol/L;

5. Patients with malignant tumor and hemorrhagic diseases;

6. Patients with serious underlying pulmonary disease;

7. Patients with serious heart disease(NYHA class Ⅲ-Ⅳ), liver disease(ALT or AST 2 times
above the upper level of normal value range), kidney disease(Cr above the upper level
of normal value range);

8. Patients who has taken Acetylcysteine in the past 3 months;

9. Patients who has taken Prednisone>15mg/day(or other equivalent amount of
glucocorticoid) and/or Immunosuppresants in the past 3 months;

10. Patients who has taken interferon, penicillamine, colchine or other agents for the
treatment of IPF;

11. Pregnant or lactating women;

12. Participated in other clinical trials in the past 1 month;

13. The investigator assessed as inappropriate to participate in this clinical trial.