Abstract: 　Objectives To explore the clinical application of deceleration capacity of rate (DC), acceleration capacity of rate (AC) and heart rate variability (HRV) in children with precardial distress of unknown origin. Methods A total of 56 children with precardial distress of unknown origin and 63 healthy children aged 6 to 17 years were examined by 24 h dynamic electrocardiogram, and the indexes of DC and HRV were compared between these two groups. Results DC value of children with precardial distress is less than that of the control group (P<0.05), AC value is greater than that of the control group (P<0.05), and heat rate (HR) is greater than that of the control group (P<0.05). No statistical differences were observed in the indexes of HRV between the two groups. The indexes of DC show a significant positive correlation with HRV in children with precardial distress(r=0.27~0.40, P<0.05), while appear a negative relation with HR (r=-0.46, P=0.000). In contrast, the indexes of AC show a significant negative correlation with HRV (r=-0.57~-0.34, P<0.05), and appears a positive relation with HR(r=0.61, P=0.000). HR valu  is higher in male children less than 12 years old with precardial distress than that of age-matched males in control group, and RMSSD is lower than the latter. DC value of male children more than 12 years with precardial distress is lower than that of age-matched males in control group, while AC value is higher than that of the latter; DC value is significant lower in female children more than 12 yeares with precardial distress than that of age-matched females in the control group (P<0.05). Conclusions The activity of vagus nerve in children with precardial distress of unknown origin is decreased. DC value is significantly lower than that of control group, and shows correlation with indexes of HRV. There is no significant difference in DC and HRV value between male and female children with precardial distress. DC value is lower in children aged 12 or older with precardial distress than that of age-matched children in the control group, which indicates adolescents are vulnerable to autonomic nerve functional disorder.