A model of intrahepatic portal hypertension was established in SD rats by injection of carbon tetrachloride (CCl4). By observing the opening angle of the portal vein, the zero-stress state of the portal veins was studied at different time during the pathogenesis of intrahepatic portal hypertension. After CCl4 injection, the opening angles of the portal veins were increased, in the tenth week, they were much greater than those in the corresponding controls (P<0.05). The results suggest that during the pathogenesis of portal hypertension, unequal remodeling exists in the portal veins to change its biomechanical properties, and the residual stress and strain of the portal veins in portal hypertensive rats are greater than those in normal controls.