Abstract: In order to understand the effect of heat treatment upon the collapse. of Eucalyptus wood,moisture contentshrinkage curves are measured and drawn in this paper by means of drying at constant temperature and various humidity for treated and untreated Eucalyptus viminalis、E. tereticornis and E.camaldulensis. The result shows that whether heat treated or not,E. viminalis and E.tereticornis have the typical"collapse pattern"moisture content -shrinkage curve.For heat treated timber of the two species,however,the second stage collapse appears rarely and the whole shrinkage and shrinkage at"shoulder point"are lower than that of untreated timber. Effect of heat treatment is apparent on E.viminalis and E. tereticornis.no effect on E.camaldulensis, This paper has introduced a two stage collapse theory and expounded for the first time that it is inevitable to appear"shoulder point"in the "collapse pattern" moisture content -shrinkage curve,and illustrated the limitation of the"indirect vessel collapse"theory presented by Shin Terazawa

Key words: Eucalyptus wood, Heat treatment, Collapse