To assess the efficacy of prenatal administration of tetrandrine (TET) on pulmonary hypoplasia in the nitrofen-induced congenital diaphragmatic hernia (CDH) fetal rat model. Six timed-pregnant female Sprague-Dawley rats were randomly divided into 3 equal groups: CDH group (receiving gavage of nitrofen 125 mg dissolved in seed fat on day 9.5), and TET group (receiving gavage of nitrofen 125 mg on day 9.5 and then gavage of TET 30 mg/kg on days 11.5 - 14.5), and control group (given the same dose of peanut oil on day 9.5 and the same dose of normal saline on days 11.5 - 14.5). The fetuses were delivered by cesarean section on day 21 to undergo light microscopy and electron microscopy. The numbers of type II pneumocytes were recorded and compared. CDH were detected in 32 of the 41 fetuses from the CDH and TET groups with a teratogenic rate of 78%, however, without a significant difference between the CDH and TET groups (P = 0.645). Microscopy showed significant lung hypoplasia in both histologic structure and cellular structure in the CDH group; however the lung development of the TET group was improved in comparison to the CDH group. There was no significant difference in numbers of type II pneumocytes among the 3 groups (P = 0.779). Prenatal administration of TET can improve the lung development of CDH rats in both histological structure and cellular structure. This may provide a new idea for the clinical treatment of CDH.