Objective:To investigate the clinical utility of carbon nanoparticles suspension as lymph node tracer in the cervical lymphadenectomy and protection function of parathyroid in patients with papillary thyroid cancer. Methods:One hundred twenty consecutive patients were divided into carbon nanoparticles suspension group(n=60) and control group(n=60) for prospective studies. All patients underwent total thyroidectomy with unilateral cervical lymphadenectomy. The operating time,operative blood loss,postoperative drainage volume,the numbers of parathyroid autotransplantation,the total number of cleaning lymph nodes(cN0 and cN1) and the diameter < 5 mm lymph node,and metastasis lymph nodes,the parathyroid hormone(PTH),the serum calcium level,and the cases of hypocalcemia after surgery were compared between the two groups. Results:The operating time was longer than that of the control group(P=0.002),operative blood loss and postoperative drainage volume had no statistically significant difference between the two groups(P > 0.05). Carbon nanoparticles suspension group cleaned out 519 pieces of lymph nodes(average 10.6),was compared with the control 293 pieces of lymph nodes(average 6.9)(P=0.000 1). In cN0 cases,the total numbers of lymph node cleaning and diameter < 5 mm lymph node with carbon nanoparticles suspension were obviously more than the control group(P=0.000 1),but in the cN1 cases,there was no difference on the total number of lymph nodes(P=0.086) between the two groups,yet it was helpful for the diameter < 5 mm lymph node inspection(P=0.000 1). Postoperative hypocalcemia of the controls was more than the carbon nanoparticles suspension group(P=0.001). Conclusion:Carbon nanoparticles suspension might help to detect metastatic lymph nodes with thyroid cancer cN0,especially diameter < 5 mm lymph node inspection,and protect the function of the parathyroid gland.