To improve organ transplantation methods, we are developing an extracorporeal organ preservation system that enables long-distance and long-term transport between donors and recipients. First, a solid model of the liver used in FEM analysis was built based on the material properties of pig livers. By analysis of deformation of this liver model in the gravitational field, we investigated whether we could explain the findings obtained by the perfusion experiment of a pig liver under multiple conditions. We considered how the stress distribution obtained by the analysis agreed with the results of the pig liver perfusion experiment, and the appropriate conditions inferred from the effect of the deflection of thin sheet holding the liver. As a result, the following two findings were obtained: (i) when the face of liver with the portal vein and artery of the liver are placed facing up on a thin flexible holding sheet, the stress of liver is reduced, which is a better state for the liver during the perfusion. (ii) The optimal quantity exists in the deflection of the thin holding sheet for holding the liver, and this optimization of deflection quantity contributes to improving the performance of the perfusion device. These results will provide guidelines for the optimal perfusion system for the human liver.