Objective To investigate the role of electrochemical detection of circulating free DNA in the diagnosis of thyroid cancer and its correlation with TI ⁃ RADS grading and clinicopathological features. Methods Circulating free DNA was extracted from plasma of 114 patients with thyroid cancer，35 patients with benign thyroid disease and 35 normal people. The current adsorption rate（ir%）of plasma free DNA（cfDNA）was detected by electrochemical method. The differences of current adsorption rate between patients with thyroid cancer，benign thyroid disease and normal people，as well as the relationship between adsorption rate and clinicopathological features and thyroid shadow were analyzed The relationship between response reporting and data system classifica⁃ tion（TI⁃RADS classification）. Results The ir value of thyroid cancer patients was higher than that of benign lesions patients（P < 0.05），AUC=0.778. The IR value of patients with thyroid cancer was higher than that of patients with benign lesions（P < 0.05），AUC = 0.778. There was no significant difference in ir between patients with benign thyroid lesions and normal controls（P = 0.094）. The sensitivity，specificity and accuracy were 61.4% ， 68.6% and 64.1%，with statistically significant differences（P < 0.05）. There was no statistically significant difference in tumor size，lymph node metastasis，local invasion and multi ⁃centrality between the ir value < 29 group and the ir value ≥ 29 group（P > 0.05）. ir value ≥ 29 was an independent risk factor for thyroid cancer OR = 1.244 （P < 0.01）. Conclusion Plasma cfDNA current adsorption rate（ir value）has certain significance in the diagnosis of thyroid cancer. The index of ir ≥ 29 is an independent risk factor of thyroid cancer. Plasma cfDNA current adsorption rate（ir value）sis correlated with TI⁃RADs grading.