ObjectiveTo detect the expression of Ki-67 in papillary thyroid carcinoma (PTC) and investigate its clinical significance. MethodsA retrospective analysis was conducted on PTC patients treated at West China Hospital of Sichuan University from August 2024 to February 2025. The relation between the Ki-67 expression in the postoperative pathological tissues and clinicopathologic features was analyzed. Additionally, the concordance of Ki-67 expression between the preoperative fine-needle aspiration samples and postoperative pathological tissues was evaluated by Bland-Altman analysis. The significance level was set at α=0.05. ResultsA total of 290 PTC patients met the inclusion and exclusion criteria were enrolled. Patients with classical PTC, M1 classification, TNM stage Ⅳ, and those achieving thyroid stimulating hormone (TSH) suppression targets at one month postoperatively had higher Ki-67 expression than those with follicular variant PTC, M0 classification, TNM stages Ⅰ–Ⅲ, or inadequate TSH suppression (all P＜0.05). No significant differences were observed in other subgroups (P>0.05). Furthermore, Bland-Altman analysis of 27 paired samples showed a mean bias of 1.269% between preoperative and postoperative measurements. Elevated variability occurred in high Ki-67 cases, with 11.1% (3/27) exceeding ±6% limits of agreement. ConclusionsThe study demonstrates that Ki-67 expression correlates with malignant attributes including tumor aggression and advanced disease. It may serve as a prognostic biomarker for assessing malignant potential in PTC.