Abstract:Three trees of Pinus tabulaeformis Carr. Were collected from a natural stand of Zhongtiao Mountains in Shanxi Province. From pith outward, the tracheid length first increases rapidly, then increases slowly after 13 years old, and levels off after 20 years old. Along the stem height, the tracheid length increases progressively from the base upward, maximum at 5.3m in height, and then decreases to the top of the tree. The shortest tracheid length was found near the crown of the trees. With augmenting age of formation of the cambial initials, the length of these cambial initials first increases, and then decreases. The tracheid diameter and the thickness of cell wall increase from pith to bark. From the base to the top of the tree, the tracheid diameter increases step by step, then decreases near the top of the tree. The radial variations of the tracheid length-width ratio and tracheid wall thickness-diameter ratio are similar to the variation of the tracheid length. Within a growth ring, the tracheid length decreases gradually from spring wood to summer wood, and then increases quickly. The tracheid length of the spring wood is shorter than that of the summer wood, and the minimum of the tracheid length is at the transitional position of the spring wood and summer wood.