As the number of implanted biventricular pacemakers increases, the coronary sinus (CS) has evoked much interest amongst cardiologists. A dilated CS could prompt the existence of many diseases. The normal CS diameter is uncertain, especially in children. A total of 446 Chinese healthy children were prospectively enrolled in this study. The superior and inferior diameter of the CS was measured from the CS ostium 1 cm from the end of ventricular systole in the modified apical 4-chamber view. Seven models were tested to determine the relationships between parameters of body size and CS diameter. Heteroscedasticity was tested by the White and Breusch–Pagan tests. A multiple linear regression model should be gender as a covariate along with BSAStevenson, in order to evaluate the influence of gender on the measurements. The formula of Stevenson was best-fit. The predicted values and Z-score boundaries for measurement of the CS diameter were calculated. Bland–Altman plot regression showed that the 95 % limits of agreement for inter- and intra-observer measurements were not significantly different. We report new, reliable echocardiographic Z scores for the CS diameter derived from a large population of healthy Chinese children. The Z scores can be used in echocardiographic examinations.