This is a randomized, controlled, double-blind, multicenter Phase 3 clinical study to assess the efficacy and safety of envafolimab plus platinum-based doublet chemotherapy versus placebo plus platinum-based doublet chemotherapy as neoadjuvant/adjuvant therapy in subjects with resectable stage IIIA and IIIB (N2) NSCLC. Primary study endpoints are MPR rate assessed by BIPR and EFS assessed by BIRC.

A total of approximately 390 participants are planned to be enrolled in this study. After being screened and qualified, the subjects will be randomly assigned to receive Envalfolimab or placebo plus platinum-based doublet chemotherapy in 1:1 ratio for a total of 3-4 cycles of neoadjuvant therapy (determined by the investigator), the feasibility of surgery is evaluated by the investigator within 4-6 weeks after the end of neoadjuvant therapy and surgery will be performed. Envafolimab (experimental group) or placebo (control group) will be administered after surgery. After completion of treatment, subjects will enter a follow-up phase, including safety follow-up, tumor disease follow-up, and survival follow-up.All randomized subjects in this study are required to receive tumor imaging evaluation as scheduled and get continuous safety assessment during the srceening and treatment period.

Inclusion Criteria:

1. Volunteer to participate and sign the informed consent form.
2. Age ≥ 18 years old, regardless of gender.
3. Histological and/or cytological diagnosis of resectable stage IIIA-IIIB (N2) NSCLC.
4. Measurable lesions based on the response evaluation criteria in solid tumors version 1.1（RECIST 1.1）.
5. Have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 1.
6. Subjects should provide tumor tissue for detection of PD-L1 expression level.
7. Sufficient organ and bone marrow function.
8. Expected survival ≥6 months.
9. The surgeon assessed that total lung function is able to withstand the proposed pneumonectomy procedure.

Exclusion Criteria:

1. Tumor histologically or cytologically confirmed or combined with neuroendocrine carcinoma components, or sarcomatous/sarcomatoid lesions, or adenosquamous carcinoma, or special pathological types.
2. Previous treatment with another drug that targets T cell receptors (e.g. CTLA-4, OX-40, etc.);
3. Participants with known EGFR mutation or ALK translocation, and non-squamous cell carcinoma subjects need to identify EGFR and ALK mutation status;
4. Upper lung sulcus tumor or locally advanced unresectable or metastatic disease.
5. Previous anti-tumor therapy for the disease.
6. Subjects with known or suspected interstitial pneumonia.Radiation pneumonia or other moderate to severe lung disease that may interfere with the detection or management of drug-related pulmonary toxicity and seriously affect respiratory function.
7. Any serious active infection.
8. With uncontrolled or significant cardiovascular and cerebrovascular disease.
9. Active autoimmune disease requiring systemic treatment.
10. Immunosuppressant or systemic hormone therapy (dose >10 mg/ day prednisone or other therapeutic hormone) for immunosuppression within 14 days prior to randomization.