Abstract: Saperda populnea is one of the important pests on poplar's branch and top in Jilin Province. The damage of this insect to Populus × xiaozhuarica cv.'Baicheng' was studied. This pest parasites on the branches with diameter less than 0.5 cm. In the early stage,92.2% of the branches will be withered and wind broken.In the late stage,11.5% of the branches with diameter less than 1 0 cm will be wind broken. When the adult insect emerges,87.4% of the invaded branches will be withered and wind broken.The gall formed by S. populnea has serious influence on the consecutive increments of branch and top. If there is one or two galls on the top of a main branch,the increment of the branch will decrease by 28.3%,16.4% and 9.8%, 42.0%, 28.9% and 17.2% respectively in the first, second and the third year. If there is one or two galls on the top of a lateral branch,the increment will decrease by 21.7%, 12.1% and 6.3%, 34.8%, 22.8% and 13.8% respectively in the first, second and the third year.