Objective：To investigate the expression of Rho kinase in fetal rats with congenital diaphragmatic hernia（CDH），and to explore the effect of Rho kinase inhibitor fasudil on lung vascular remodeling. Methods：Timed-pregnant SD rats were randomly divided into control group（5 rats），CDH group（6 rats） and fasudil intervention group（6 rats）. Nitrofen of 100 mg was given to by gavage CDH and intervention group for establishing CDH models and olive oil of the same dose was given to the control group. At day 16.5 of gestation，fasudil（15 mg/kg，qd，for 3 consecutive days） was given via intraperitoneal injection to the intervention group，while Ns was given to by the same way control and CDH group. All fetal rats were delivered by cesarean in fixed time. The small pulmonary arterial morphologic changes in all groups were analyzed with microscopy. The gene and protein expression of Rho kinase were respec－tively examined by RT-PCR and Western blot；the phosphory－lation of myosin binding subunit（MBS） of myosin phosphatase-a substrate of Rho kinase was detected by Western blot as a marker of the activated kinase. Results：Morphometry investiga－tion showed that the ratio of small pulmonary artery wall thick－ness to vascular external diameter（WT%） and the medium thickness percentage（MT%） were significantly increased in CDH group than those in control group[（26.88±2.41） vs. （13.50±1.45）；（25.59±2.57） vs. （16.47±2.07），P=0.000]. The ratio of small pulmonary vascular lumen area to the total area（LA%） in the CDH group was markedly lower than that in the control group[（39.22±2.23） vs. （61.20±3.23），P=0.000]. However，compared with those in the CDH group，WT% and MT% in the intervention group were significantly lower [（15.38±2.14） vs. （26.88±2.41）；（17.69±1.79） vs. （25.59±2.57），P=0.000] and LA% was higher[（58.67±3.06） vs. （39.22±2.23），P=0.000]. The expression of Rho kinase mRNA and Rho kinase protein was significantly higher in the CDH group than in the control group（P=0.000）. The phosphorylation of MBS was also significantly higher in the CDH group（P=0.000）. Compared with those in the CDH group，expressions of Rho kinase mRNA and protein and the phosphorylation of MBS were significantly reduced in the fasudil intervention group（all P<0.01）. Conclusion：Lung vascular remodeling is confirmed in fetal rats with CDH and Rho/Rho kinase signaling pathway may be involved in. Prenatal fasudil treatment may obviously improve the lung vascular remodeling in fetal rats with CDH.