In spite of the economical and sivicultural importance, tending methods of natural broad leaf tree have not been established in Korea. In the present study, the structure of crown and biomass of Quercus variabilis were analyzed to obtain the basic information on pruning practice. There was not correlated between clear length of sample tree and tree height and D. B. H. The stratum with the largest leaf and branch weight was lower part of the stratum with the largest branch increment. The degree of contribution of branch to knotless trunk production (Δω_B(Z)/ω_B(Z) and ω_L(Z) /ω_B(Z) ) decreased from the upper part to the lower part. As an example of the application of the ecological data to pruning practice, the author attempted to estimate the effect of pruning with this experimental stand. Two methods of pruning were investigated. One is the removal of branches according to a definite external indication such as clear length rate of branch, and the other is the removal of barnches according to a definite height.