This clinical trial aims to evaluate the efficacy and safety of neoadjuvant therapy with Limertinib Followed by Sintilimab and Chemotherapy in resectable Stage II-IIIB EGFR-Mutant NSCLC. Untreated stage II-IIIB NSCLC (AJCC 8th edition) patients assessed as surgically resectable by investigators will be randomized 1:1 into the experimental or control group after signing informed consent and meeting eligibility criteria. All patients receive Limertinib for 6 weeks. Within 7 days thereafter, imaging assessment will be performed. If no progression is observed, experimental group patients discontinue therapy for 1 week, then receive Sintilimab + Carboplatin/Cisplatin + Pemetrexed every 3 weeks for 3 cycles; control group patients receive Limertinib for 9 weeks and Carboplatin/Cisplatin + Pemetrexed every 3 weeks for 3 cycles. Preoperative tumor assessment is required. Surgery will be performed 2-6 weeks (±7 days) after the first dose of the final cycle. Then patients will recieve 2-year adjuvant Osimertinib starting 1 month post-surgery. If imaging assessment after 6 weeks of limertinib treatment shows lesion enlargement but remains confined to stage II-IIIB, the investigator will decide whether the patient continues study treatment or not; if progression occurs to unresectable stage III or advanced disease, the patient must discontinue. The primary endpoint is pathological complete response (pCR) rate.