Object To analyze the clinical value of prenatal ultrasound in diagnosis of congenital diaphragmatic hernia(CDH). Methods 75 cases of CDH and 40 cases of normal fetus were retrospectively analyzed. And the lung-to-head ratio(LHR) and fetal middle cerebral artery were compared in two groups. Results In 75 cases, 68 located on the left and 7 on the right. 44 cases were in the second trimester and 31 in third trimester. However, 35 cases combined with other Prenatal ultrasound featuresmalformations, including cardiovascular system malformation, nervous malformations, urogenital system malformation, skeletal system malformation, and etc. In all cases, 33 showed LHR＞1.6 , 20 in LHR＜1.0 , and 22 in LHR between 1.0 and 1.6. Middle cerebral artery flow velocity was significantly lower in fetuses with CDH than in healthy fetuses (29.03±0.22 VS 42.11±0.17cm/s, P＜0.001), however there were no significant difference in PI and RI (1.50±0.19 VS 1.43±0.13, P＞0.05; 0.73±0.16 VS 0.76±0.23,P＞0.05).Conclusion Prenatal ultrasound can accurately diagnose CDH, Which is often associated with other malformations, we need pay more attention to every system of the fetus, especially cardiovascular system. In addition to, obtaining the lung-to-head ratio and middle cerebral artery flow with CDH may provide more information for prenatal management and intervention after birth.KEY WORDS congenital diaphragmatic hernia；ultrasound；prenatal；fetus