Abstract: Effects of mixed forest on immature larvae population dynamic of N. xiangyunicus arc studied in this paper. The results show that the happening period is seriously longer with immature larvae population incrown at mixed forest, there isn’t a serious dynamic oflarvac populattion by increasing with hard spread trend and continuing about 20 days, but it’s an aggregated pattern, compared with pure forest. The spread in space and the increase in quantity of pest population arc restrained in mixed forest, therefore the happening and damage of pest are restrained, the space separating of forest phase and the number of kinds with feeding plants of forest pest are main superficial reasons.