Objective To detect the expression of KiSS-1 protein in papillary thyroid carcinoma, and to analyze its significance. Methods Paraffin-embedded specimens of 32 patients with thyroid papillary carcinoma and its adjacent cancer tissues were included in this study. Then the expression of KiSS-1 protein was detected by munohistochemistry and its relationship with clinical pathological features was analyzed. Results KiSS-1 protein mainly expressed in the cell membrane and cytoplasm. The expression of KiSS-1 protein was positive in adjacent tissues, but decreased or absent in cancer tissues in 32 patients. In the latter, there were 11 cases with positive expression (34.4%) and 21 cases with negative expression (65.6%), and the difference was statistically significant (χ2=31.256, Plt;0.001). The average value of KiSS-1 protein expression represented by absorbance (A) value (119.595 2) in cancer tissues was higher than that in adjacent tissues (174.805 0), t=34.429, Plt;0.001. The expression of KiSS-1 protein in cancer tissues was not related to patient gender (P=0.618) and age (P=0.061), but except TNM staging (P=0.034). The expression rate of KiSS-1 protein in cancer tissues with lymph node metastasis (4/4, 100%) was significantly higher than that without lymph node metastasis (7/28, 25.0%)， P=0.003. Conclusion The expression of KiSS-1 protein is decreased or absent in papillary thyroid carcinoma, which may be involved in tumorigenesis, invasion, and metastasis.