ObjectiveTo evaluate the value of parathyroid hormone (PTH) in predicting hypocalcemia at different time after thyroidectomy. MethodsThe literatures in CBM, WanFang, CNKI, VIP in Chinese, and OVID, PUBMED, EMBASE, and MEDLINE in English were searched. Hand searches and additional searches were also conducted. The studies of predicting hypocalcemia after thyroidectomy by detecting postoperative PTH at different time were selected, and the quality and tested the heterogeneity of included articles were assessed. Then the proper effect model to calculate pooled weighted sensitivity (SEN), specificity (SPE), positive likelihood ratio (LR+), and negative likelihood ratio (LR-) were selected. The summary receiver operating characteristic (SROC) curve was performed and the area under the curve (AUC) was computed. ResultsTwenty-three articles entered this systematic review, 21 articles were English and 2 articles were Chinese. Fifteen of 23 articles were designed to be prospective cohort study (PC) and 8 of 23 articles were retrospective study (Retro). These articles were divided into two groups. Group 1 was the studies of detecting postoperative PTH in 1 hour, which included 2 012 cases (494 of them occurred hypocalcemia). Group 2 was the studies of detecting postoperative PTH between 4-12 hours, which included 693 cases (266 of them occurred hypocalcemia). The publication bias of 2 groups were smaller that founded through the literature funnel. Meta analysis showed that in addition to merge SEN, between the 2 groups with merge SPE, LR+, LR-, and AUC differences were statistically significant (P < 0.01);the forecast effect of group 1 was better than group 2, and the AUC was the largest area when the PTH value in 1 hour after operation was below 16 ng/L. ConclusionDetection of postoperative PTH value is an effective method for predicting postoperative hypocalcemia. The 1 hour after operation for detecting PTH value below 16 ng/L to predict postoperative hypocalcemia have the best effect.