Abstract: The relative crystallinities in three regions (compression. transition and opposition region) of compression wood of Masson pine (Pinus massoniana) have been determined with the method of X-ray diffraction analysis, and the results of the measurement have been analysed with the theory of thermodynamics; The study showed that the crystallinity distribution in different zones of compression wood follows certain regularities which are caused by the following factors; (1) intrinsic growth mechanism of trees, (2) enviromental temperature of growth, (3) compression and tension state of trees.

Key words: Compression wood, X-ray diffraction, Crystallinity