Objective: To examine the plasma fibroblast growth factor-23 (FGF-23) concentration in children with primary hypertension and to investigate the association between plasma FGF-23 and subclinical cardiovascular damages,and to identify its predictive value for diagnosis. Methods: With prospective study,77 patients (61 males and 16 females) who were diagnosed as primary hypertension with the average age of (11.8±2.2) years were enrolled with informed consent in Children's Hospital,Capital Institute of Pediatrics from October 2016 to December 2017. Carotid wall intima-media thickness (cIMT) measured by Doppler ultrasound and left ventricular hypertrophy (LVH) identified by echocardiography were assessed as parameters of subclinical cardiovascular damages. Patients were divided into increased cIMT group (n=18) and normal cIMT group (n=46) (64 patients with complete data of cIMT). According to left ventricular geometry,patients were divided into LVH group (n=27) and normal geometry group (n=50). Concentration of plasma FGF-23 was detected in all children by enzyme linked immunosorbent assay test. Mann-Whitney U test was used to compare plasma levels of FGF-23 between groups. Kendall's tau-b correlation coefficient was used to analyze the correlation between plasma FGF-23 and cIMT/LVH. Receiver operating characteristic (ROC) curve was used to analyze the value of plasma FGF-23 in the prediction of subclinical cardiovascular damage. Results: The concentration of plasma FGF-23 in the increased cIMT group was higher than that in the normal cIMT group (55.6 (46.2,63.5) vs. 48.6 (39.4, 57.3) ×10(3) RU/L, Z=-2.143, P=0.032) . Also, plasma FGF-23 showed positive correlation with cIMT(r=0.222, P=0.032). According to ROC curve analysis,the cutoff value of plasma FGF-23 for prediction of increased cIMT was 53.9×10(3) RU/L (55.6% sensitivity and 71.7% specificity). The concentration of plasma FGF-23 in the LVH group was significantly higher than that in normal geometry group (55.0 (46.8, 65.7) vs. 48.2 (39.5, 56.0)×10(3) RU/L, Z=-2.375, P=0.018). And,plasma FGF-23 was correlated positively with LVH (r=0.224, P=0.018). The concentration of plasma FGF-23 in patients with concentric remodeling (n=10) was significantly higher than that of the normal geometry group (56.9 (49.6, 66.3) vs. 48.2 (39.5,56.0) ×10(3) RU/L, Z=-2.093, P=0.036). According to ROC curve analysis,the cutoff value of plasma FGF-23 for prediction of LVH was 49.1×10(3) RU/L (70.4% sensitivity and 60.0% specificity). Conclusion: The concentration of plasma FGF-23 in children with primary hypertension was correlated positively with LVH and cIMT and had certain predictive value of diagnosis for subclinical cardiovascular damages.