Objective To investigate the diagnosis and differential diagnosis of benign and malignant thyroid lesions with CT signs. Methods The imaging data of 48 patients with thyroid diseases were collected. The patients were divided into benign group and malignant group according to benign and malignant lesions. Compared with postoperative pathological diagnosis, the effectiveness of CT in the diagnosis of benign and malignant thyroid diseases was evaluated, and CT imaging characteristics of the two groups were analyzed. Results Operation and pathology showed 27 cases of benign lesions and 21 cases of malignant lesions while CT examination showed 26 cases of benign lesions and 22 cases of malignant lesions. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of CT in the diagnosis of benign and malignant thyroid lesions were 92.6%, 96.8%, 96.2%, 93.8% and 94.8%, respectively. The majority of benign thyroid lesions were multiple nodules. The nodules were with clear edges and shape, even density and intact thyroid capsule and without grit-like calcification. There was no lymph node enlargement in most patients. However, there was no significant difference in the density and degree of cystic degeneration between benign and malignant nodules. Conclusion CT can be used in the examination of benign and malignant thyroid lesions. It is of high diagnostic value and is worthy of clinical application.