Objective To evaluate the protective effect of adiponectin in early atherosclerosis and the diagnostic value of adiponectin in metabolic syndrome in obese children. Methods Total 176 obese children and 88 normal weight children aged 9-12 years were included in the present study. All participants underwent hematologic and biochemical tests including serum adiponectin, high sensitivity C-reactive protein (hsCRP),fasting blood glucose, insulin, and plasma lipids. Homeostasis model assessment of insulin resistance (HOMA-IR)was calculated. Noninvasive ultrasound measurement including intima-media thickness of the common carotid artery(IMT), brachial flow-mediated dilatation (FMD), carotid artery compliance (CAC), and the maximum fatthickness ahead of peritoneum (Pmax) were obtained to investigate arterial mechanical properties and endothelial function. Results (1) The level of adiponectin was negatively correlated with obese index, blood pressure,fasting insulin, hsCRP, HOMA-IR, and IMT(P<0.05 or P<0. 01 ); but not with triglyceride, fasting blood glucose, CAC, high-density lipoprotein-cholesterol (HDL-C), and FMD. (2) The risk of metabolic syndrome increased 3.43 times in children with adiponectin level <7. 060 mg/L compared with ＞7. 060 mg/L. (3)Receiver operating characteristic( ROC ) curve was used to choose the optimal cutpoint of adiponectin to identify obese children with the metabolic syndrome. The area under the curve (AUC) for adiponectin to discriminate the sensitivity of metabolic syndrome was 0. 769 (95% CI0. 714-0.816, P< 0. 0 1 ). (4) The obese children were divided into three groups according to the cut-off value for adiponectin (high, middle, low groups). There were significant differences in the prevalences of severe obesity, visceral fat accumulation, hypertension, insulinemia,low HDL-C, metabolic syndrome among three groups (P<0.05). Conclusions High levels of serum adiponectin could prevent early stage of atherosclerosis. The lower the adiponectin level, the higher the incidence of metabolic syndrome.