Objective To investigate the expressions and clinical significance of Notch-2 protein and Numb protein in papillary thyroid carcinoma (PTC). Methods PTC tissues and its para-cancerous tissues of 50 patients with PTC who treated in The Affiliated Hospital of Inner Mongolia University for Nationalities from Mar. 2014 to Mar. 2017 were retrospectively collectied, to detect the expressions of Notch-2 protein and Numb protein by immunohistochenmical method. Results ① Expressions of Notch-2 protein and Numb protein in PTC tissues and para-cancerous tissues: the positive-expression rate of Notch-2 protein in PTC tissues was 82.00% (41/50), which was higher than that of para-cancerous tissues〔18.00% (9/50)〕, the difference was statistically significant (χ2=40.960, P<0.001). The positive-expression rate of Numb protein in PTC tissues was 66.00% (33/50), which was higher than that of para-cancerous tissues 〔0 (0/50) 〕, the difference was statistically significant (χ2=49.254, P<0.001). ② The relationship between expression of Notch-2 protein and expression of Numb protein in PTC tissues: there was a positive correlation between expressions of Notch-2 protein and Numb protein in PTC tissues (rs=0.323, P=0.022). ③ The relationship between expressions of Notch-2 protein and Numb protein in PTC tissues and clinicopathological features of the PTC patients: the expression of Notch-2 protein in PTC tissues was not significantly correlated with gender, age, tumor diameter, capsule infiltration, cervical lymph node metastasis, and TNM staging (P>0.05). The expression of Numb protein in PTC tissues was not significantly correlated with gender, age, tumor diameter, and capsule infiltration (P>0.05), but was significantly correlated with cervical lymph node metastasis and TNM staging (P<0.05), the positive rates of Numb protein in patients of staging Ⅲ+Ⅳ group and cervical lymph node metastasis group were lower than those of patients in staging Ⅰ+Ⅱ group and non-cervical lymph node metastasis group. Conclusion The positive-expression rate of Notch-2 protein and Numb protein in PTC tissues are higher than those of para-cancerous tissues, and there is a positive correlation between them in PTC tissues, suggesting that there may be a synergistic effect in the course of PTC progression.