The radial variation law of velocity of sap flow in the trunk of Ligustrum lucidum in Sep.~Nov.2009 was studied systematically by thermal diffusion method.The results indicated that the velocities of sap flow at different depths in the trunk of L.lucidum in autumn showed low-high-low variation trend from the outside toward the center,the daily variation trends of velocity of sap flow at different depths were same basically,the velocity of sap flow at the depth of 20 mm was highest,that at the depth of 30 mm...