Abstract: natural stands were selected respectively from 6 provinces in the main distributing regions of P. davidiana Dode and 20 trees were sampled randomly from each plot.5 among the 20 trees were cut for standard test of wood quality characteristics and the other 15 trees with the increment cores drilled out increment cores at DBH, which are used for contrast and supplemental test. The results of the analysis are as follows:(l)Both wood specific gravity and fiber length of cores agree with those dataum attained by the test of the felled trees. (2)Wood specific gravity and fiber length among annual ring groups of intra-tree are increasing with the increase of tree age,and conform to S curving line and Sanio regularity,whose variations are significant at 0.0l level. The maximum point of relative increasing rate of wood specific gravity and fiber length appear between 11a and 20a,6a and l5a,respectively.(3)Correlation of wood specific gravity of junenil-eadult is slightly different from that of fiber length.It is suggested that early selection of main wood quality characteristics should be carried out during 10～15a.