Abstract: The degree of relative crystallinity of the wood cellulose in the stem of Pinus massoniana Lamb. Was determined by means of X-ray diffraction and infrared spectra. The relative crystallinity (CrI%) of the fomer is 53.8%, but the infrared ratio (NO'KI and O'KI) of the latter is 0.45 and 1.12 respectively. The moisture absorptivity of the ball-milled sample exposed for seven days at 65% R.H. and at the room temperature is about 11—13%.The relative crystallinity determined by X-ray diffraction method was found simpler and more reproducible than by infrared spectra method. The correlation of X-ray diffraction with NO'KI is better than with O'KI and a few relevant regression equations are also given.