Objectives To establish normative reference ranges of fetal cardiac dimensions between 20 and 34 per weeks including: inner diameter of fetal heart and arteries, aortic arch isthmus, descending aorta, ducts artery and foramen ovale.Simple regression analysis was applied to assess possible correlation between cardiac diameter and gestational age.Methods A cross-sectional study was undertaken on singleton pregnancies with normal fetuses and accurate gestational ages.Totally 2573 normal fetus was divided into 15 groups according to the gestation.According to United States Association of echocardiography guidelines and standards for fetal echocardiography, all measurementswere stored to statistic the normal reference value range and analyze the correlation of these measurementsand gestation age.Results 1.Concluded the normal reference value of the fetal cardiac cavity diameter and the anatomy structure.We found that in normal fetus, the measurement values of fetal cardiac structures increases as gestational age advanced from 22 to 28 weeks and has statistics differences (P<0.01) , including and fetal thorax cross diameter, heart cross diameter, left atrial and the right atrial diameter, left ventricle and the right ventricle diameter, aortic and pulmonary artery.But aortic arch isthmus, descending aorta, left pulmonary, and right pulmonary, ducts artery and foramen ovale diameter although increased as gestational age advanced, without clear statistic significance (P > 0.05).2.The ratio relationship between the diameter of the fetal cardiac Anatomy: in the pregnant 20-34 weeks, the diameter of right atrium, right ventricle is always greater than the diameter left atrial and left ventricular; the diameter of pulmonary artery is always greater than the diameter of the aorta; the diameter of aortic arch isthmic diameter is always greater than the diameter of ducts artery (P < 0.01 =.The diameters of the left pulmonary artery and right pulmonary artery are equal during the pregnancy.The diameter of ducts arteryis always greater than the diameter of left pulmonary artery and right pulmonary artery.3.Simple regression analysis of correlation between cardiac meter and gestational age: With the advance of gestation a significant curve increase in fetal thorax cross diameter, heart cross diameter, left atrial and the right atrial diameter, left ventricle and the right ventricle diameter, aortic and pulmonary artery, aortic arch isthmus, descending aorta, left pulmonary, and right pulmonary, ducts artery was found.Conclusions Fetal echocardiography technology can accurately assess fetal cardiac structure; the establishment normal reference value of cardiac cavity diameter could provide guidance to fetal echocardiography examination; all measurements have curve increasecorrelation with gestational age.