Objective: To detect the methylation status of ribosomal S6 kinase 4 (RSK4)in papillary thyroid carcinoma (PTC)and to study its correlation with mRNA expression and clinical features. Methods: 134 cases PTC tissues and corresponding paracancerous thyroid tissues were collected. DNA methylation status of RSK4 gene in PTC tissues and corresponding paracancerous tissues were analyzed by methylation specific PCR and bisulfite genomic sequencing, and mRNA expression was detected by quantitative realtime PCR. The relationship of DNA methylation status with mRNA expression and clinical features was analyzed. Results: The methylation rate of RSK4 in PTC tissues was significantly higher than that in paracancerous tissues by methylation specific PCR (P<0.05)and bisulfite genomic sequencing (P<0.01). The RSK4 mRNA level in PTC tissues was significantly lower than that in paracancerous tissues (P<0.01). In PTC tissues, RSK4 mRNA expression in methylation group was lower than that in unmethylation group (P<0.01). The RSK4 mRNA level in PTC of methylation was lower than that in paracancerous tissues of methylation (P<0.01); the RSK4 mRNA level in PTC of unmethylation was also lower than that in paracancerous tissues of unmethylated ones (P<0.01). There was relationship of RSK4 hypermethylation with lymphatic metastasis and TNM grade (P<0.05). Serum concentrations of thyroid stimulating hormone, thyroid peroxidase antibody, and thyroglobulin antibody in methylation group were higher than those in unmethylation group (P<0.05). Conclusion The hypermethylation of RSK4 promoter′s CpG islands might be one of the mechanisms for poor expression of RSK4 in PTC, which may serve as a molecular target of early diagnosis and treatment.