Abstract: The mean microfibril angle of Pinus massoniana was measured by means of diffractometer technique using(002)reflection.The methods of X-ray diffraction are easy to measure.The wood samples can be free from the modification as a result of chemical treatment.The comparison between the mean microfibril angle measured by iodine staining and the values obtained by (002)reflection was studied.The former is somewhat smaller than the latter. Because the mean microfibril angle of Pinus massoniana is smaller than 20°,M₄₀ agrees well with M_(0.6t).Since the longer the tracheid the steeper will be the pitch of the helices of the microfibrils to the longitudinal axis of the fiber, the mean microfibril angle of latewood is smaller than the earlywood,and the mean value of sapwood is larger than the heartwood.