The purpose of this study is to determine whether Triptergium wilfordii, and Acitretin are effective and safe in the treatment of patient of moderate to severe psoriasis vulgaris.

Inclusion Criteria:

• Adults of both sexes, between the age 18 and 75 years.
• Have a diagnosis of psoriasis vulgaris,PASI score of 7 or greater.
• Capable of giving informed consent and the consent must be obtained prior to any study related procedures.

Exclusion Criteria:

• Currently have erythrodermic,guttate or pustular psoriasis.
• Have any active dermatoses which may affect disease assessment of psoriasis.
• Have used any investigational drug,any biologic or any systemic immunosuppressants within the previous 1 month..
• Have used topical medications/treatments that could affect psoriasis or PASI evaluation (eg, corticosteroids, tar, phototherapy et al.) within 2 weeks.
• Have any acute or chronic or recurrent infectious disease,which was difficult to control.
• Have the history of HBV or HCV infection,or HIV antibody test positive.
• AST, ALT or blood fat levels must be within 1.5 times the ULN range for the laboratory conducting the test.
• Are pregnant, nursing, or planning pregnancy in the coming two years(both men and women) while enrolled in the study.
• Have any severe systemic disease or have a history of malignancy.
• Have shown a previous hypersensitivity to Triptergium wilfordii or Acitretin.
• Have any other condition not suitable to join in trial,which are judged by investigator.