In this paper,three species of Eucalyptus wood were subjected toheat treatment by means of softening with hight temperature and lowering pre-sure instantaneously,The result showed that,except longbeak Eucalyptus,after heat treatment pit membrances on the vessel walls of Eucalyptus woodgot broken to some extent,or even holes appeared as the membrances broppedout.Thus,permeability of the treated、 wood got improved noticeably.Of thetested conditions,140℃ and 5 hours treatment Produced the best result.