25 clones(6 trees from each clone) were sampled (aged 15 years) from clone test stand of Populus tomentosa. The fiber forms (fiber length, fiber width, ratio of fiber length and fiber width, fiber wall thinckness, fiber lumen diameter, ratio of 2 fiber wall thinckness and fiber lumen diameter, ratio of fiber lumen diameter and cell diameter) were analysed. Variance analysis showed that these 7 traits were significantly different among clones at 0.05 level. 2 characters, Fiber width and fiber lumen diameter, were strongly inherited, and others 5 traits were under moderate genetic control. The selection could be conducted effectively among clones. The variation analysis of microfibrillar angles showed that there was significantly difference among clones at 0.05 level. The clones repeatability (0.961) and single repeatability (0.651) of microfibrillar angles indicated that the character was under genetic control. And selection could be conducted effectively among clones and within clones. The variance analysis of transverse section tissue percentage include vessel percentage, fiber percentage and wood ray percentage of Populus tomentosa were perfected. All traits except vessel percentage were observed significant clonal differences at 0.05 level. The values of clone repeatability of vessel percentage and fiber percentage were 0.437 and 0.336 separately, and the values of clone repeatability of wood ray percentage was 0.711. This showed that genetic control for wood ray percentage is feasible.
