Inclusion Criteria:  Patients with active AAV met the criteria of 1990 ACR and 2012 Chapel Hill criteria Age 18 to 75 years Written informed consent obtained before taking part in the study  Exclusion Criteria:  Severe AAV defined as potentially organ- or life-threatening disease (i.e. alveolar haemorrhage, heart failure caused by myocarditis or pericarditis, progressive neurological symptoms, deaf, blindness, et al.) Serum creatinine>120umol/L or proteinuria>1.0g/d Receipt of a JAKi therapy previously Co-existence of another systemic autoimmune disease Secondary vasculitis (following neoplastic disease, an infection or antithyroid drugs) Malignancy or history of malignancy Infection by HIV, HCV, HBV or tuberculosis- Severe uncontrolled cardiovascular, pulmonary, liver, gastrointestinal, endocrine, hematological, neurological, or psychiatric diseases that are not related to systemic vasculitis Allergic to JAKi Blood dyscrasias including confirmed: Hemoglobin <9 g/dL or Hematocrit <30%; White blood cell count <3.0 x 109/L; Absolute neutrophil count <1.5 x 109/L; Platelet count <100 x 109/L; Alanine transaminase or aspartate aminotransferase or total bilirubin>1.5 upper normal limit; Estimated glomerular filtration rate<60ml/min/1.73m2 Incapacity or refusal to understand or sign the informed consent form. Pregnancy, breastfeeding.