Objective To study the CT in the diagnosis and differential diagnosis of benign and malignant thymoma application value. Methods Retrospective analysis in March 2010 to September 2015, 24 patients with malignant thymoma and 35 patients with benign thymoma clinical medical records, observation of patients with benign and malignant thymoma CT signs, discusses its application in the diagnosis and differential diagnosis of benign and malignant tumors. Results CT detection rate is 100% of benign and malignant thymoma, 35 cases of benign tumors were complete capsular, edge smooth, 3 cases of pleural thickening. 24 patients with malignant thymoma coated are incomplete, rough edges, 16 cases of pleural thickening and pleural effusion. Low-risk group, high-risk groups and thymic carcinoma tumor size, shape, the density of mediastinal fat layer and comparison, the differences were statistically significant (P<0.05). Conclusion CT for benign and malignant tumor diagnosis good sensitivity, high accuracy, in benign and malignant tumor and its subtypes, with a high application value in the differential diagnosis of clinical treatment for has important guiding significance.