The purpose of this study is to evaluate the efficacy and safety of Jaktinib in participants with moderate to severe atopic dermatitis.

The study is divided into two stages, the first stage test (1-12 weeks): the main test; the second stage test (13-24 weeks): the extended test.

The main test：The trial set up 4 treatment groups, including 3 dose exploration groups, Jaktinib 50mg Bid, 75mg Bid, 100mg Bid group and 1 placebo control group.

The extended test：Subjects in the placebo group were randomly assigned to receive Jaktinib 50mg Bid, 75mg Bid, and 100mg Bid treatments at a ratio of 1:1:1 (randomized in a blinded state and completed by IWRS in the background), the main test group (50mg Bid, 75mg Bid, 100mg Bid group) subjects still maintain the original dose after 12 weeks.

Inclusion Criteria:

• Meet the Chinese diagnostic criteria for atopic dermatitis (Zhang's criteria) and be diagnosed as atopic dermatitis.
• Participants must have moderate to severe AD at screening and randomization.
• Participants must have inadequate response to topical medications within 6 months of screening.
• Agree to use emollients daily

Exclusion Criteria:

• Received prior treatment with any oral Janus kinase (JAK) inhibitor less than 4 weeks prior to randomization.
• Have received certain types of vaccinations.
• Participants who do not agree to use adequate contraception during the trial and within 4 weeks after the last dose.
• Any Participants whom the investigator deems inappropriate for participation in this clinical study