This is a phase II, prospective, multi-centre study. To assess the efficacy and safety of furmonertinib in patients with epidermal growth factor receptor 20ins mutation positive stage IB-IIIA Non-small Cell Lung Carcinoma, following complete tumour resection with or without adjuvant chemotherapy. The study plans to enroll 20 subjects, treating with furmonertinib 160mg/d, until disease recurrence, death or intolerability. The maximum duration of treatment is three years. The primary endpoint is DFS. The secondary endpoint include DFS rate , OS and the change of HRQoL. In addition, the peripheral blood ctDNA will be collected and analyzed in this study