Purpose To evaluate transabdominal color doppler ultrasound in diagnosing fetal arrhythmia in the first trimester. Materials and MethodsTotal 11956 women with common pregnancy were submitted to diagnosed whether they were fetal arrhythmiawith transabdominal color doppler ultrasound during 12-14 gestation. Analyze the types of arrhythmia with combination of color doppler and M-mode of ultrasonic methods and observe whether they were with complicated structural abnormality. The results of transabdominal color doppler ultrasound were comparedwith autopsy after induced labor or echocardiogram after born. Results 12 cases with fetal arrhythmia were diagnosed by transabdominalultrasound(0.1%,12/11956), of which 9cases were sinus tachycardia, 2 cases were bradycardia(atrioventricular heart -block),1 case were atrial extrasystole. Half of the fetal arrhythmia cases were combined with fetal abnormalities, including 4 cases of congenital heart diseases,1 case of limb body wall complex, 1 case of hydrops fetal. Allof the 6 cases were termination of pregnancy. Follow-up results were consistent withSprenatal diagnosis. Conclusion Transabdominal color doppler ultrasound can contribute to early detection of fetal arrhythmia and structural abnormalities,and provide important reference for early clinical intervene and manage.