Abstract: Based on the 28 years old Castanopsis hystrix in Laohuling test plantation to research the heartwood variation characteristics,and then studied quantitatively the change rule of heartwood forming process by evaluating the relationship between heartwood and sapwood from regression equation.The results were as follows:The initial age of heartwood was estimated to be 717a,heartwood forming rate was 072 rings per year after heartwood occurred in trunk.The linear relationship between diameter of heartwood and sapwood was more significant than linear relationship between annual rings:y=10219x-81766,R2=0978.Heartwood formation should occur until radial and axial distribution of sapwood was wider than 800 cm, and the sapwood increased 100 cm in diameter while the heartwood increased 102cm. Heartwood stem fullness showed a positively correlated with increasing of diameter.The HW/SW(both in diameter and annual)and the time of heartwood formation decreased with increase of height.