Abstract: Objective:To investigate the value of CT plain scan and enhancement in the diagnosis and preoperative evaluation of papillary thyroid carcinoma. Methods:Data of 46 patients with papillary thyroid carcinoma were collected, and CT features of plain and enhanced scans were analyzed for preoperative evaluation. The lymph node metastasis to the size and location of primary focus and the relationship between primary focus and thyroid capsule were analyzed. Results:CT plain scan can clearly showed the primary focus, combined with enhanced scan and coronal or sagittal reconstruction, it can further clarify the relationship between the tumor and the surrounding tissue structure and metastasis. In this group, 60.3% of the lesions were irregular, 46.7% of the patients had microcalcification, 87.0% of the patients showed marked enhancement, and the range of focus became smaller than before enhanced scan. There was statistical significance between the central lymph node metastasis and the cervical lymph node metastasis with the location of the primary focus(P=0.023), also there were statistical significance in the size of primary focus and the relationship with thyroid capsule between the lymph node metastasis group and the non metastasis group(P<0.05). Conclusion:The diagnostic rate of papillary thyroid carcinoma can be significantly improved by analyzing the characteristics of CT plain scan and enhancement, such as the focus shape, micro calcification, enhancement mode and the change of focus range before and after enhancement. Also the range of resection and lymph node dissection can be rational determined by comprehensive evaluation of primary focus, peripheral invasion and lymph node metastasis. In addition, we found there were a certain correlation between lymph node metastasis and he size and location of primary focus and the relationship between primary focus and thyroid capsule.