This study is to evaluate the efficacy and safety of an antifibrotic agent, pirfenidone as treatment of systemic sclerosis. The primary outcome of this study is improvement of skin fibrosis.

All patients enrolled should suffer from moderate to severe skin fibrosis at the screening stage.

The study period is 52 week. The study contains two stages, a 24-week blind stage following with open stage for another 24-week period of time. Subjects will receive pirfenidone or placebo randomized in the first 24-week and will all receive pirfenidone treatment in the second 24-week, with of combination of low dose steroids.

The secondary outcomes of this study include but not limit to safety, improvement of lung fibrosis and digital ulcer burden.

Inclusion Criteria:

• Fulfill EULAR/ACR classification criteria (2013) for systemic sclerosis (SSc).
• Subjects must have mRSS≥10 at screening stage
• Subjects must have signs of fibrosis in their chest CT at screening stage
• If a subject has received treatments before, it should be stable at least 3 months until screening and with no significant efficacy (ΔmRSS≤-2)

Exclusion Criteria:

• Subjects with other connective tissue diseases overlapping with SSc
• Subjects with skin atrophy as the main cutaneous manifestation
• Subjects with active digital ulcers or gangrene
• Active severe SSc-driven renal disease or heart dysfunction at screening
• Subjects with significant hematologic abnormalities
• Abnormal liver function test at screening (ALT, AST or total bilirubin over 2 fold of upper normal level
• Clinically significant active infection including ongoing and chronic infections
• History of human immunodeficiency virus (HIV)
• Confirmed Positive tests for hepatitis B or positive test for hepatitis C
• Active tuberculosis
• Live or attenuated vaccine within 4 weeks prior to screening
• Subjects with significant hematologic abnormalities