Objective To investigate the clinical value of three-phase dynamic contrastenhanced scanning in the diagnosis of right upper lung cancer and mediastinal lymph node metastasis. Methods From January 2015 to August 2016, 56 cases of patients with lung cancer undergoing CT scan and three-phase dynamic contrast-enhanced scan in our hospital were studied. The clinical and imaging data of 56 patients were collected. Two experienced diagnostic radiologists evaluated CT scan and enhanced scan, and analyzed the imaging features and metastasis of lung cancer. Results The pathological examination showed that all 56 patients had single lung cancer, of which 38 patients had mediastinal lymph node metastasis. The detection rate of lung cancer in CT scan was 94.64% in 56 patients. Among them, 13 cases were diagnosed as squamous cell carcinoma, 18 cases were adenocarcinoma, 13 cases were small cell carcinoma and 9 cases were mixed adenocarcinoma. 32 patients with mediastinal lymph node metastasis, the diagnosis rate was 84.21%. There was no significant difference between the CT scan and the pathological findings of the right upper lung cancer (χ2 =22.267, P=0.079). In the right upper lobe of the lung, the lesion area in the third phase of dynamic contrast-enhanced enhanced imaging was significantly enhanced, and the surrounding tissue and mediastinal lymph node metastasis was clearly demonstrated. Conclusion Three-phase dynamic contrastenhanced computed tomography (CT) images of the upper right lobe of the lung showed more prominent changes in the structure of the right upper lobe, which can directly and completely display the lesion area and find the mediastinal lymphatic metastasis in time, which is beneficial for the imaging doctor to accurately locate the lesion site Display, can provide important clinical imaging information to help clinicians diagnose, guide clinicians to develop the correct treatment program, it is worth clinical promotion and application.