Abstract:The pine sawyer beetle, Monochamus alternatus Hope, is not only a main vector of Bursaphelenchus xylophilus, but also an important stemboring pest of pines in our country. The feeding habit of the adults and larvae was clarified preliminarily by observations both in laboratory and in the field, and the relationship was expounded between the adult damage and physiological weakness of pine, the larvae boring and pine dying. The relationship between the larvae and other stem-boring pests was also studied at the same time. The egg-depositing habit of the adult and the pattern of population distribution of the larvae were discussed. The authors Consider that the adult and larvae feeding are may be the most important factors among the causes inducing pine dying in our country. In order to prevent pine trees from dying in vast area, the numeral increase of the species group of pine sawyer beetle adult attention be the most important factors paid must to.