• Participants are able to understand the informed consent form, voluntarily agree to participate, and sign the informed consent form;

• Participants must be 18 years or older and under 75 years of age on the day they sign the informed consent form;

• Pathologically confirmed stage IB (AJCC TNM staging, 8th edition) lung adenocarcinoma;

• Achieved complete resection (R0) after lobectomy, bilobectomy, or sleeve resection;

• Pathologically diagnosed as grade 3 invasive lung adenocarcinoma according to the 2020 grading system proposed by the International Association for the Study of Lung Cancer (IASLC) Pathology Committee (poorly differentiated: any tumor with 20% or more of high-grade patterns, including solid, micropapillary, and/or complex glandular patterns);

• No prior receipt of any anti-tumor treatment, including but not limited to systemic chemotherapy, immunotherapy, or radiotherapy;

• Expected survival time more than 12 weeks;

• No active EGFR mutations (including but not limited to exon 19 deletions, exon 21 L858R, exon 21 L861Q, exon 18 G719X, or exon 20 S768I mutations) or ALK rearrangements;

• Tumor PD-L1 expression ≥1% (the PD-L1 IHC 22C3 pharmDx reagent, antibody clone number: 22C3, detection platform: DAKO Autostainer Link 48);

⁃ Patients are screened and enrolled within 4 to 12 weeks after surgery;

⁃ Performance status score of 0 or 1 (Eastern Cooperative Oncology Group (ECOG) performance status scale);

⁃ For female participants of childbearing potential, a negative serum pregnancy test must be obtained within 7 days prior to the first dose of the study drug;

⁃ Female participants of childbearing potential or male participants with partners of childbearing potential must agree to use highly effective contraception (with an annual failure rate of less than 1%) starting from 7 days before the first dose of the study drug and continuing until 24 weeks after the last dose;

⁃ Major organ functions must be normal within 7 days prior to the first dose of the study drug.