Objective：To analyze the clinical features and prognosis of immune checkpoint inhibitor-related pneumonitis（CIP）in lung cancer. Methods：Clinical data of lung cancer patients who developed CIP after receiving immune checkpoint inhibitor（ICI） treatment at the First Affiliated Hospital of Nanjing Medical University from September 2018 to September 2022 were retrospectively collected. Baseline characteristics，clinical features，treatment conditions were analyzed and described，and survival analysis was conducted. Results：A total of 75 patients were included，with 71 males and 4 females，with a mean age of（66.7±7.6）years. The onset time was 4 to 1 054 days after receiving ICI treatment. 60.0% of patients had pre-existing emphysema at baseline，and 36.0% had interstitial lung abnormalities（ILA）/interstitial lung disease（ILD）. Radiological manifestations included organizing pneumonia（OP） type，nonspecific interstitial pneumonia（NSIP）type，acute interstitial pneumonia（AIP）/acute respiratory distress syndrome（ARDS） type，and other types，with 36 cases（48.0%），28 cases（37.3%），6 cases（8.0%），and 5 cases（6.7%），respectively. There were significant differences in survival between patients with pre-existing ILA/ILD at baseline and those with CIP manifested as AIP/ARDS type（P < 0.05）. Conclusion：Lung cancer patients with pre -existing ILA/ILD before receiving ICI treatment and CIP manifested as AIP/ARDS type have a poorer prognosis.