Abstract: In order to correctly estimate the mean number of the larvae of Dendrolims kikuchii Mats.in per tree of Keteleeria evelyniana Mast.and at the same time reduce the difficulty,labour and time consumption in sampling,the number of the larvac in the lowest branch from the tree trunk is used as an auxiliary factor x to estimate the number of larvae in the whole tree.The regression relation between the mean number of larvae per branch x and the mean number of larvae per tree y is obtained as y=-1.94+10.51x.The correlation coefficient between x and y is r=0.97.F test shows very significant linear relationship between x and y.The optimum numbers of sampling unit are also given in this paper.