Objective To investigate the correlations of complement C5a and tumor necrosis factor alpha (TNF-α) with insulin resistance by observing changes in clinical indicators of obese children with or without insulin resistance. Methods Children aged 7-14 years were enrolled in this study from the pediatric endocrine clinic of the Second Affiliated Hospital of Xi'an Jiaotong University from September 2014 to September 2016.All participants were divided into obesity with insulin resistance group (n=60), obesity with non-insulin resistance group (n=46) and control group (n=40).Physical data, levels of blood lipid, fasting blood glucose (FBG), insulin, TNF-α and complement C5a were tested.And the correlation of HOMA-IR and clinical indicators were analyzed. Results Body mass index (BMI) and waist circumference were significantly higher in the obese group and the insulin resistance group compared with normal control group and non-insulin resistance group (P＜0.001).Tri-glyceride(TG), FBG and insulin levels were significantly higher in insulin resistance group than those in non-insulin resistance group(P＜0.001), and HDL-C level was lower in insulin resistance group(P＜0.001).However, there was no significant difference on the level of total cholesterol (TC) among three groups(P＞0.05).The levels of TNF-α and C5a in the obesity group were significantly higher than those in the normal control group(P＜0.001).Difference on TNF-α level between the two groups were not significant, while C5a level was significantly higher in obesity with insulin resistance group than that in obesity without insulin resistance group (P=0.456).Multivariate regression analysis showed that BMI, waist circumference, FBG, TNF-α and C5a levels were positively correlated with insulin resistance (β=0.413, 0.234, 0.268, 0.318, 0.400, P＜0.05). Conclusions The inflammatory indicators like TNF- and C5a levels are closely related to insulin resistance index.BMI, TG, FBG, TNF-α and C5a levels may be independent risk factors for insulin resistance.