This study is to evaluate the safety, tolerability, pharmacokinetics and efficacy of RSS0393 topical ointment in the treatment of plaque psoriasis in children and adolescents.

Inclusion Criteria:

1. Age ≥ 6 years old and < 18 years old at screening.
2. History of plaque psoriasis ≥ 3 months.
3. The subjects and their parents or legal guardians voluntarily signed informed consent before any study-related procedures began.

Exclusion Criteria:

1. Diagnosis of psoriasis other than plaque at screening.
2. Subjects have other skin diseases or conditions that may affect the evaluation of the relevant endpoints of this study.
3. Subjects with any other persistent active autoimmune disease.
4. Subjects who have received topical medication for psoriasis within 14 days before baseline, or systemic medication or phototherapy for psoriasis within 28 days before baseline, or biological agents for psoriasis within a specified time before baseline.