With the continuous development of computer visualization technology and laser technology, “Digital Forestry” in China is being moved forward steadily. As a new mapping technology, three-dimensional (3D) laser scanning can quickly obtain the 3D model of the target，and therefore it has been initially applied in the survey of forest resources, study on the stand structure and 3D reconstruction of single tree. To explore the accuracy of the technique in forest mensuration, the measurement accuracy of 3D laser scanning technology is analyzed through the experiments in forestry and the factors which affect the scanning accuracy are summarized. The results show that the model constructed by the scanning data has a higher precision: the average error of scanning diameter at breast height (DBH) is -0.16%, the average error of scanning tree height is -0.35%, and the average error of scanning basal area is -0.11%. The errors meet the precision requirements of forestry completely. The technology has the adaptability and application prospects in the field of conservation of old and rare trees, forest resource inventory and forest cutting.