【Objective】The article aimed to study the variation principles of height-diameter ratios of trees,to provide a theoretical basis for reasonable density control of plantation management.【Method】The Pinus massoniana plantations in different areas were selected for stand survey and trunk analysis.Statistical analysis,graphical analysis and model analysis were conducted to explore the relationship between tree height,DBH,age and height-diameter ratio,study the variation law of the height-diameter ratio under different site index levels and fore...