Objective: To evaluate the performance of the inferior vena cava collapse index(IVC-CI) measured by ultrasound on predicting supine hypotension syndrome (SHS) in parturients following spinal anesthesia. Methods: A total of 102 single-fetus parturients scheduled for cesarean section were prospectively enrolled in the study. The inferior vena cava maximal diameter during quiet expiration (IVCe) and expiration(IVCi) in both supine and left lateral position were measured by ultrasound to calculate IVC-CI and IVC-CI in different position(ΔIVC-CI) sprior to spinal anesthesia. The ΔIVC-CI was deduced to represent the impact of postural change. The parameters including IVCe, IVCi, IVC-CI and ΔIVC-CI were compared between parturients with and without SHS. Result: Fifty-four parturients presented SHS after spinal anesthesia. The parturients were predisposed to lower IVCe and IVCi, and higher IVC-CI in supine position than left lateral position(P<0.01). There was no difference in IVCe, IVCi and IVC-C of parturients between with and without SHS in left lateral position(P>0.05). The IVCe and IVCi measured in supine position were lower, and IVC-CI in supine position and ΔIVC-CI were higher in parturients with SHS (P<0.01). The areas under ROC curve (AUC) of IVC-CI and ΔIVC-CI for prediction of SHS were 0.941 and 0.927. With the cutoff value of 41.43% and 14.09%, the sensitivity and specificity of IVC-CI and ΔIVC-CI for predicting SHS in supine position were 88.9% and 98.8%, and 87.0% and 87.5%, respectively. Conclusion: The IVC-CI measured in supine position and ΔIVC-CI by ultrasound prior to spinal anesthesia could be used to assess the risk of incidence of SHS.