Objective：To evaluate the clinical value of prenatal ultrasound in detecting fetal septum pellucidum abnormalities and compare it with MRI. Methods：Fifty-two cases of fetal clear septum abnormalities detected by prenatal ultrasound were compared with MRI findings, The diagnostic coincidence rate of the two methods was analyzed, all cases were followed up for prenatal diagnosis and pregnancy outcome, and follow-up neonatal nervous system development .Results：Among the 52 fetuses with abnormal septum pellucidum, 7 had enlarged septum pellucidum(13.46%),the transparent septum was small in 7 cases (13.46%) , the transparent septum was not shown in 35 cases (67.31%)and 3 cases (5.77%) had abnormal shape of septum pellucidum. The coincidence rate of ultrasound and MRI was 39 cases (75.00%) , and that of non-coincidence was 8 cases (15.38%),SMRI was complementary to ultrasound findings in 5 cases (9.62%). Both ultrasound and MRI showed abnormal septum pellucidum in 44 cases, 23 cases were isolated hyaline septum abnormality(52.27%),there were 7 cases of narrow, 6 cases of wide, 10 cases did not show. 21 cases(47.73%) had abnormal septum pellucidum with associated malformation, there were 17 cases not shown, 3 cases with abnormal shape, 1 case with widening. Nineteen of them were associated with central nervous system malformation , Complete absence of the corpus callosum was found in 12 cases . Chromosome analysis , except for one case (Case 3)amniocentesis CMA revealed chromosome 15 abnormalities, the other 51 cases were normal .Analysis of pregnancy outcome, 13 cases induced labor, 1 case lost to follow-up, the remaining 38 cases continued pregnancy . The newborn was followed up for 6 months, except for 1 case (case 15) with delayed development of nervous system, the other 37 cases had no obvious nervous system abnormality. Conclusions：Prenatal ultrasound is the main method for screening fetal Septum pellucidum abnormalities and associated anomalies, MRI is an important complementary examination, Especially the observation of fetal cerebral cortex development has a greater advantage. Prenatal identification of isolated clear septum abnormalities or associated anomalies is essential for fetal evaluation, the prognosis of the fetus with isolated hyaline septum abnormality is better.