Abstract: During the winters of 1987 and 1988, 29 sample sites of Pinus massoniana were selected in Susong County and Qianshan County of Anhui Province, and population densities of Dendrolimus punctatus were investigated according to a designed method. Through the analysis of the data, we obtained the following results:(1) The caterpillars thoroughly enter into the state of overwintering at the end of December.(2) In young trees, nearly all the caterpillars overwinter in the clumps of the needles; in higher trees, nearly ail the caterpillars go down to the crevices of the bark to overwinter, and most of them conceatrate on the lower-parts of the trunks under 2 m. The percent cf the number investigated from the lower-parts of the trunks under 2 m to the number from the whole tree (p) is related to the population density of the sample sites (g), the regression model is p=97.76-3.67√q.