Inclusion Criteria:1. Participants must be between 18 and 75 years old when signing the informed consent form (ICF), regardless of gender; 2. Confirmed diagnosis of plaque psoriasis for at least 6 months at screenin 3. Disease is stable at screening and baseline visits, and the following criteria are met:

• Static Physician Global Assessment (sPGA) score ≥3;
• Psoriasis Area and Severity Index (PASI) score ≥12;
• Body Surface Area (BSA) affected by psoriasis ≥10%; 4. Deemed by the Investigator as suitable for systemic therapy or phototherapy; 5. Women of childbearing potential must have a negative pregnancy test at screening and baseline visits. Women of childbearing potential and male trial participants whose spouse or partner is a woman of childbearing potential must be willing to use at least one effective method of contraception as specified in the protocol during the study period (from signing the ICF until 30 days after the last dose of investigational drug). Male trial participants must also commit to not donating sperm during the study period and within 30 days after the last dose of study drug; 6. Before initiating any screening or study-specific procedures, trial participants must be able to understand and willing to comply with all protocol requirements, and voluntarily sign and date the ICF.

Exclusion Criteria:1.Presence of non-plaque psoriasis during the Screening period or at the Baseline visit; 2.Past or current diagnosis of drug-induced psoriasis; 3.Concomitant other autoimmune diseases, including but not limited to rheumatoid arthritis, sarcoidosis, and systemic lupus erythematosus; 4.Receiving therapeutic agents for psoriatic arthritis (PsA) other than stable-dose non-steroidal anti-inflammatory drugs (NSAIDs) or analgesics.

5.Prior exposure to TQH3906 Capsules or Deucravacitinib Tablets; 6.Receipt of any of the following medications or treatments within the specified time window:

1. Any topical agents or treatments that may interfere with psoriasis assessment, administered within 2 weeks before the Baseline visit;
2. Psoriasis phototherapy administered within 4 weeks before the Baseline visit;
3. Any biologics or biosimilars thereof, administered within the specified time frame before the Baseline visit;
4. Systemic non-biologic psoriasis therapy and/or systemic immunosuppressive treatment administered within 4 weeks before the Baseline visit; 5) Within 6 months prior to the baseline visit: Leflunomide; 6) Within 4 weeks prior to the baseline visit: Traditional Chinese medicines (TCM), Chinese proprietary medicines, or herbal preparations used for psoriasis treatment or with unknown composition/nature, including but not limited to Total Glucosides of Paeony, Tripterygium wilfordii preparations, Compound Glycyrrhizin preparations, Compound Qingdai preparations, etc.; 7) Within 4 weeks prior to the baseline visit: Any live vaccines or live-attenuated vaccines; OR anticipated need to receive live vaccines or live-attenuated vaccines during the study period including at least 4 weeks after the last dose of investigational product; 8) Within 3 months prior to the baseline visit (or 5 half-lives, whichever is longer): Investigational biological agent treatment; OR within 30 days prior to the baseline visit (or 5 half-lives, whichever is longer): Any other investigational drug treatment; OR currently participating in other clinical trials; 7. Active infection/history of infection, or receipt of specific anti-infective therapies within the specified time windows; 8. Previous or current presence of severe or unstable diseases or medical conditions involving neurological, cardiovascular, respiratory, digestive, urinary, hematological, or immune systems that, in the Investigator's judgment, may interfere with outcome assessment or affect participation safety 9. Laboratory test abnormalities meeting any of the following criteria during the screening period: 1) Hemoglobin <90.0 g/L; 2) White blood cell count <3.0×10⁹/L; 3) Neutrophil count <1.0×10⁹/L; 4) Lymphocyte count <0.5×10⁹/L; 5) Platelet count <100×10⁹/L; 6) Alanine aminotransferase (ALT) and/or Aspartate aminotransferase (AST) >3× Upper Limit of Normal (ULN); 7) Total bilirubin (TBIL) >1.5× ULN; 8) Estimated creatinine clearance <45 mL/min calculated based on the Cockcroft-Gault formula. (See Appendix 2 for calculation formula); 9) Thyroid-stimulating hormone (TSH) outside the normal reference range, concomitant with free T4 or T3 also outside the normal reference range.

10. History of drug or alcohol abuse within 6 months prior to screening; 11. Known allergy, hypersensitivity, or intolerance to TQH3906 capsules, deucravacitinib tablets, or any excipient ingredients; 12. Women who are pregnant, breastfeeding, or planning to become pregnant during the trial, and men who plan to father children or donate sperm during the trial; 13. Trial participants who are employees of the Sponsor, third-party agency staff, or direct research center staff involved in this study or their family members; 14. Per Investigator assessment, presence of any other medical, psychiatric, or other reasons that render the trial participant unsuitable for participation in this study.

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