The mechanical properties of the hepatic artery that is more than 0.1mm in diameter are initially studied in the paper. The equation D/D0= A' + B'p shows the relationship between the internal pressure p and the dimensionless parameter D/Do in physiological normal range. And elastio deformation constant of the hepatic artery is obtained. Uhder centai high pressure, the hepatic artery is obviously deformed and appeared to be vessel cirsoid.