Spatial structure of forest between different forest age of Eucalyptus plantations were compared by the method of spatial instead of time. the results were showed as followed ： there great differences between different Eucalyptus plantations. The growth speed of plantations were very rapid in the 1 -5 year old,and were presented by logarithm growth. With the increase of forest age canopy density and litter （ including litter thickness and litter cover percentage ） of the plantations both increased and then decreased. Hiberarchy of different forest age of Eucalyptus plantations were clear, their dominant plant were all nearly identical, however the quantity and distributing span（individual size, number, species number） of undergrowth plants in different constituent layers were changed from increase and decrease to increase as forest age of plantations as was increased. It was also showed that spatial structure of different forest age plantations could significantly differentiated by cluster analysis.
Forestry Science and Technology of Guangdong Province
Eucalyptus, plantation, Spatial Structure of Forest, undergrowth plant