Abstract: The structures of Qinghai spruce (Picea crassifolia) forests in Dayekou watershed on the northern slope of Qilian Mountains were studied along the altitude from 2 500~3 300 m, and the values were calculated with sub-segment elevation (per 100 m a. s. l.). The results are as follows. (1) The forest density was high while the trees were relatively small in the study area. The forest density, DBH, H and crown diameter of stands were 1 550 ± 628 trees·hm-2, 13.9 ± 6.2 cm, 8.1 ± 3.7 m and 3.3 ± 1.7 m, respectively. With the elevation increasing, the forest density, the average DBH and the crown diameter decreased. The average H showed a "unimodal" change. (2) The saplings (DBH 5~12.5cm) and middle trees (DBH 12.5~22.5cm) were predominant in the forests, and the height of trees were about 6~12 m. With the elevation increasing, the percentage of seedlings (DBH≤5 cm) in forest showed a basic stability, the percentage of saplings decreased slightly, the percentage of middle trees showed a "unimodal" change, which peaked at 2 800~2 900 m a. s. l., the percentage of big trees (DBH>22.5 cm) increased. The percentage of the stands (H≤6 m) showed a "V" shaped change, which the minimum value appeared at 2 800~2 900 m a. s. l.. The percentages of the stands (H: 6~12 m) and the stands (H >12 m) showed "unimodal" changes, peaking at 2 600~2 700 m and 2 800~2 900 m a. s. l., respectively. (3) The ratio of height to diameter ranged from 0.45~0.73 and the breast-height basal area ranged from 7.86~33.32 m2· hm-2, with the elevation increasing, both of them showed a "unimodal" change, which peaked at 2 800~2 900 m a. s. l.. Analysis shows that the stand density, moisture and temperature conditions were leading to the differentiation of the growth in tree diameter and height. The middle segment elevation (2 800~2 900 m a. s. l.) is the most suitable area for Qinghai spruce forests distribution in this area.