ObjectiveTo summarize the variation of parathyroid hormone (PTH) after thyroidectomy and the influence factors of postthyroidectomy hypocalcemia (PHC). MethodsClinical data of 95 patients who underwent thyroidectomy in Affiliated Shengjing Hospital of China Medical University from Jan. 2015 to Dec. 2015 were analyzed retrospectively. ResultsOf the 95 patients, there were 27 patient (28.42%) suffered from PHC (PHC group), and levels of serum calcium in the other 68 patients (71.58%) were normal (normal group). There was no significant difference in levels of serum calcium and PTH between the PHC group and normal group before operation (P > 0.05), but levels of serum calcium and PTH in PHC group were both lower than corresponding index of normal group after operation (P < 0.05). The levels of serum calcium and PTH both decreased in PHC group after operation (P < 0.05), and only PTH level decreased in normal group after operation (P < 0.05). PHC was related with type of operation, who underwent two-side operation had higher risk of PHC (P < 0.05), but there was no significant relationship between PHC and gender or age (P > 0.05). ConclusionsPTH is an important factor for PHC. In addition, it is easier to occur PHC when the operative range become bigger.