Eucalyptus nitens (Deane & Maiden) Maiden has positioned itself as an alternative species for the creation of forests of rapid growth, tolerant to a wide range of environmental conditions. A large supply of high quality products is expected by implementation of intensive thinning and pruning, which will increase the economical values and profitability obtained from this plantations. The present study aims to evaluate the effect of thinning on the basic density of E. nitens wood, and to model the basic wood density according to log height. The experiment was carried on an E. nitens stand located in Arauco, Central Chile. A factorial model with three levels was used as the experimental design for evaluation of the effect of residual stand density on basic wood density. The main factor is the residual stand density and the treatments are 1100 (without thinning), 800 and 400 trees/ha using three repetitions per treatment. For the modeling of basic wood density, regression models of segmented polynomial were utilized. Eight years after thinning the results showed that it did not have significant effect in the E. nitens basic wood density. On the other hand, modeling basic wood density reached acceptable and consistent levels when the segmented model was used to adjust the average by relative height class.