To obtain normal range of coronary artery diameter with body surface area (BSA) dynamic changes in normal children at different age. The left main coronary artery (LCA), left anterior descending artery (LAD), left circumflex artery (LCX) and the right coronary artery (RCA) diameter were measured in 400 normal subjects from Chinese population aged 0 d to 18 years [(6.43 ± 4.45) years], using HP Sonos 5500 color Doppler ultrasonic system, according to the standard method of measuring the coronary artery diameter. (1) The diameters of LCA, LAD, LCX and RCA in different age groups (0 d-12 months, -3 years, -6 years, -9 years, -12 years, -18 years) had significant differences (F = 61.688, 51.343, 46.375, 50.192, P < 0.01,all groups mean differences had significant differences, there was significant difference between every two groups, P < 0.05), there were no significant differences between male and female subjects (P > 0.05). (2) The correlation analyses showed that the diameter of LCA, LAD, LCX and RCA had significant linear correlations with age, height, weight and BSA (r ranged from 0.71 to 0.85, P < 0.01 ). (3) The regression analyses were respectively performed on the diameters of LCA, LAD, LCX and RCA with BSA to establish seven regression models. The coefficients were compared for each model, the best model was chosen to create a Z score calculator, tracing out the Z value curve, through clinical practice,we chose Z score within ± 2 as the coronary artery diameter's normal range for Chinese children. Coronary artery diameter's Z score curve is effective and reliable, it provide objective basis for clinicians and sonographers to accurately and quickly diagnose the anomalies in diameter of coronary artery.