This study includes a dose escalation part(phase I) and a dose extension part(phase II).

In phase I of this study, a multi-center, randomized, placebo parallel control design was adopted. Enrolled subjects were randomly assigned to the experimental group or the placebo group.A total of 40 subjects are expected to be enrolled in about 4 centers.

In phase II of this study, a multi-center, randomized, double-blind parallel, placebo-controlled design was adopted. Enrolled subjects were randomly assigned to the experimental group or the placebo group.About 120 subjects are expected to be enrolled in about 10 centers.

Inclusion Criteria:

• 18 ~ 65 years old (including boundary value), regardless of gender;
• Diagnosis of Alopecia Areata;
• Hair loss accounts for 5% ~ 49% of the total scalp area;
• The duration of hair loss is at least 6 months, the longest is not more than 5 years;
• Patients can complete treatment for at least 6 months;
• About Fertility needs meet the following criteria: The results of serum pregnancy tests performed by fertile women during screening visits must be negative, and the results of human chorionic gonadotropin tests performed before the initiation of the study drug must be negative;Women who were fertile and men who had not received vasectomies were required to use effective contraception throughout the study period beginning with the informed consent and up to six months after the last administration;
• Subjects will voluntarily participate in the study after learning about the content and potential adverse drug reactions and must sign an IRC-approved informed consent prior to beginning any examination required by the study;
• Subject is willing and able to comply with scheduled visits, treatment plan, study drug administration, and other study procedures.

Exclusion Criteria:

• The following causes of hair loss should be excluded: hair loss caused by androgenic alopecia,syphilis, thyroid diseases, etc.
• Acute Diffuse and Total Alopecia of the Female Scalp;
• Prior history of serious chronic diseases, such as thyroid disease, liver disease, malnutrition, heart disease, nervous system disease, gastrointestinal dysfunction, tumor and mental illness, etc;
• Human immunodeficiency virus infection, hepatitis C virus infection, hepatitis B virus infection;
• Participated in a trial for a topical or oral JAK inhibitor;
• Allergic reactions to active ingredients or excipients are known or determined by the investigator;
• Receipt of treatment known to potentially affect the course of AA within last 3 month;
• In the opinion of the investigator , the subject is inappropriate for entry into this study.