Abstract: Objective: To explore the value of body surface electrocardiogram(ECG) in the diagnosis of secundum atrial septal defect complicated with right ventricular hypertrophy in children.Methods: The ECG of 183 children with secundum atrial septal defect were observed.All cases were divided into the secundum atrial septal defects complicated with right ventricular hypertrophy group and without right ventricular hypertrophy.The 8 indexes of ECG between two groups were compared,the sensitivity,specificity and accuracy rate of whose were calculated,respectively.Results: Between two groups,the difference of the detection rate of ECG shaft starboard was not statistically significant(P>0.05),but the differences of the detection rates of other 7 electrocardiographic indexes were statistically significant(P<0.05 to P<0.01).The results of ECG showed the sensitivities and specificities of VATV₁>0.03 s and V₅ S/R>1.0 were 87.10% & 45.45% and 93.39% &19.35%,respectively.The Q(q) wave in lead V₁ or R>2.0 mV and notched on R wave in three inferior leads and incomplete right bundle branch block were found,the accuracy rates of whose were 74.32%,75.96% and 71.58%,but their specificities were 85.12%,84.30% and 86.78%,respectively.The specificity and accuracy rate of 3 joint indexes were 98.35% and 73.77%,respectively.Conclusions: The diagnostic effect of a single index of ECG on secundum atrial septal defect complicated with right ventricular hypertrophy is not ideal,the diagnostic effect of joint index is better.