【Abstract】 Objective To evaluate the correlation between the Subxiphorid Inferior Vena Cava (IVCSP) and Transhepatic Inferior Vena Cava (IVCTH) and investigate the diagnostic value of IVCTH in assessment of the volume status and fluid responsiveness in mechanical ventilated patients. Methods A study was made in 67 mechanical ventilated patients who were extracted from the ultrasonic database between March 2015 and June 2015. All the patients were both measured the IVCSP and IVC TH through twodimensional echocardiography. The correlation and consistency was analyzed between the data of two different position. In addition, the distensibility index of the IVC (dIVC) was calculated as the ratio of IVCSP［（IVCmaxIVCmin）/IVCmin］ and expressed as a percentage to predict the consistency and cutoff value of the distensibility index of IVCTH. Results There was a correlation between the IVCSP and IVCTH (r=071, P＜005) and poor consistency for volume status assessment (Kappa value: 05475). On volume status assessment, IVCTH＜138cm indicated hypovolemia (optimized sensitivity was 8333%, specificity was 2295%). IVCTH＞21cm indicated that the volume was overload (sensitivity was 3333%, optimized specificity was 8361%). On volume responsiveness assessment, when the cutoff value was 14%, the sensitivity was 7187% and specificity was 8286%. When the cutoff value was 5%, the optimized sensitivity was 8750% and specificity was 3429%. When the cutoff value was 23%, the sensitivity was 7187% and optimized specificity was 8286%. Conclusion There was a good correlation between IVCSP and IVC TH in mechanical ventilated patients. The distensibility index had a good diagnostic value for volume responsiveness assessment and different cutoff values can be used to optimize sensitivity and specificity.