Abstract: The life history of Monochamus alternatus was observed and comparatively studied at 12 localities in Yunnan Province by field observation, trace investigation and wood dissection in order to control the beetle M. alternatus and to prevent pine wilt disease caused by the nematode Bursaphelenchus xylophilus. It was showed that M. alternatus occurred one generation with 5 intar larvae each year in Yunnan Province and overwintered in xylem of the pine trees by 3-4 instar larvae. The adult stage of M. alternatus lasted from late March to early June. The egg stage lasted from mid April to mid July. The underbark larva stage lasted from late April to mid October. The insidexylem larva stage lasted from late July to mid June of the coming year. The larvae transferred from underbark to inside xylem from late July to middle October, and began to pupate from early March to late June. The development process of the beetle differed from place to place and that was mainly influenced by air temperature. The process postponed successively from southwestern to northeastern direction in Yunnan Province. The best time for felling the pine trees infested by M. alternatus was from December to the coming January of the next year.