Objective The aim of the study was to evaluate the relationship between portal hypertension and ligation of left portal vein ( LLPV), together with the possible role of NO in prehepatic portal hypertension ( PHT). Methods Thirty-six 8-week-old SD rats were divided into six groups: LLPV with needles of 0. 6, 0. 7, or 0. 8 mm in diameter; ligation of the main portal vein (LMPV) with a needle of 0. 9 mm in diameter; left lateral lobe of liver ligated and removed (LLLR); and sham operation. The portal vein pressure (PVP) was measured in all rats before the operation, immediately after the operation, and 15 and 30 days after the operation. All rats were sacrificed 30 days after the operation. The portal vein blood, and left and right lobes of liver tissues were saved to measure the concentration of NO. Results For rats in the LLPV group, the PVP levels immediately, 15 days, and 30 days after the operation were all significantly higher than the preoperative PVP and PVP of the sham operation group at the same time. No statistically significant difference of PVP was found between the LLPV group with a needle of 0. 6 mm in diameter and the LMPV group 30 days after the operation. There were also no significant differences of the NO concentration in left and right lobes of liver tissue and blood in all groups. Conclusions LLPV can also form stable PHT. A needle of 0. 6 mm in diameter can acquire good result . NO does not play a role in prehepatic PHT.