OBJECTIVE: To determine the association between heart rate variability (HRV) and hypertension in Chinese children. METHODS: The study was conducted in First Hospital of Jilin University, China. A total of 101 children were recruited in this study. They were divided into a high systolic blood pressure (SBP) group (HS group) and normal SBP group (NS group) according to the SBP levels. In the second set of experiments, the children were divided into a high diastolic blood pressure (DBP) group (HD group) and normal DBP group (ND group) according to the DBP levels. HRV measurements were performed, and the time domain and power spectrum values were calculated. FINDINGS: The differences of low frequency (LF)/high frequency (HF) ratio, HF, and standard deviation of normal-to-normal RR intervals (SDNN) between daytime and nighttime were obviously abolished in HS and HD groups. The HS group displayed significantly lower values of HRV over a 24 h period compared to the NS group (SDNN, standard deviation of the averaged normal-to-normal RR intervals [SDANN], Triangle Index, root mean square successive difference [RMSSD], total power [TP], ultra-LF [ULF], and HF). Only the Triangle Index in the HD group was lower than that in ND group. CONCLUSION: We provide evidence that HRV is reduced and the circadian rhythm of HRV is weakened in hypertensive children, and hypothesize that a reduced HRV is a potential pathophysiological mechanism linking childhood hypertension and adulthood cardiovascular diseases.