Bartter’s syndrome (BS) is a severe tubulopathy causing renal salt- wasting, severe polyuria, dehydration, failure to thrive and secondary hyperaldosteronism. The incidence is about 1 in 1,000,000. It is an autosomal recessive disorder caused by inactivating mutations in genes that encode membrane proteins of the thick ascending limb of the loop of Henle. Diagnosis is usually made postnatally by a laboratory test or becomes evident when polyuria appears to the baby. Ultrasound findings are nonspecific without apparent fetal or placental abnormalities, thus it is difficult to suspect the disease. Here we report a case of 33-year-old nulliparous woman who was referred to our center at 31 weeks’ gestation because of severe polyhydramnios. The patient had underwent twice amnioreduction of 2L at 27 and 30 weeks of gestational age, respectively. At the time of visit, the amniotic fluid index was 44.12cm. Small stomach and enlarged liver were observed, thus esophageal atresia with tracheal esophageal fistula was suspected. Persistent right umbilical vein was also observed. Karyotyping showed no specific chromosomal abnormality. At our center, 3 amnioreductions were performed with a total fluid volume drainage of 8.4L (2.5L at 31weeks, 3L at 33weeks, and 2.9L at 35weeks of gestation). During the whole pregnancy period, total of 12.4 L of amnioreduction was done. After an uneventful antenatal period, a 2.21kg male baby was delivered by cesarean section at 36+1weeks of gestation. Laboratory test of the baby showed hyponatremia, hypokalemia and elevation of plasma renin and aldosterone. In addition, the baby showed a sign of polyuria. Therefore, with presumptive diagnosis of BS, genetic test was done and the result is pending. In summary, we report a rare case of prenatally diagnosed BS. When unexplained severe polyhydramnios is suspected, biochemical assessment of amniotic fluid may provide clue to the diagnosis. Our report may provide informative data for this rare disease.