Objective To study the diagnostic value of glycosylated hemoglobin(HbA1c)combined with ho-meostasis model assessment of insulin resistance( HOMA-IR)in obese children with prediabetes. Methods Five hundred and ninety-five obese children diagnosed at Outpatient Department of Pediatrics,Tianjin Medical University General Hospital were enrolled in the study from October 2012 to March 2016. Oral glucose tolerance test(OGTT)and HbA1c test were performed after fasting 8 to 10 hours for all the subjects. According to the World Health Organization (WHO)criteria,the obese children were divided into non-prediabetes group(483 cases)and prediabetes group(112 cases). The levels of HOMA-IR and HbA1c were compared between 2 groups. The receiver operating characteristic (ROC)curve was drawn for screening prediabetes,and the diagnosis value of area under curve( AUC)and different cutoff value were calculated. Logistic regression model was used to analyze the combined diagnosis of prediabetic AUC with preserved probability as a single variable and ROC curve. Z test was used to compare the statistical differences of each AUC. Results The levels of HbA1c and HOMA-IR of the prediabetes obese children group[(5. 65 ± 0. 36)%and 11. 60 ± 8. 86]were all higher than those of the non-prediabetes obese children group[(5. 47 ± 0. 32)% and 6. 49 ± 4. 61],and there were significant differences between 2 groups(all P<0. 01). The AUC of HbA1c ROC for prediabetes was 0. 633. When the cutoff was 5. 585%,the sensitivity and specificity were 0. 584 and 0. 601,respective-ly. The AUC of HOMA-IR ROC for prediabetes was 0. 758. When the cutoff was 7. 244,the sensitivity and specificity were 0. 779 and 0. 669,respectively. When combined with HOMA-IR and HbA1c,the AUC was 0. 764. Compared with HbA1c,there were significant differences in AUC of ROC curve between HOMA-IR alone or HOMA-IR com-bined with HbA1c in the diagnosis of prediabetes mellitus(all P<0. 01). There was no significant difference in AUC of ROC curve between HOMA-IR alone and HOMA-IR combined with HbA1c in the diagnosis of prediabetes melli-tus(P>0. 05). Conclusions Only HOMA-IR or HOMA-IR combined with HbA1c may be the optimal indexes for diagnosing obese children with prediabetes.