Abstract:Through the observation of *Monochamus alternatus* raised in the lab, trapped by baiting wood, collected from dissected sample trees, or gathered by trapping apparatus, the paper makes a research on their occurrence period at altitudes in the range of 400～1200 meters in Enshi. The study shows that the occurrence period of *Monochamus alternatus* adults is from the end of April to middle October. The adult eclosion peak is gradually postponed when the altitude increases. The eclosion peaks of *Monochamus alternatus* adults living within 400～600m, 600～800m, 800～1000m, 1000～1200m above sea level are late June, early July, middle July, and late July respectively. The generation of *Monochamus alternatus* at different altitudes all occurs in a year. The young larvae and old larvae live through the winter in their tunnels of the phloem and xylem respectively. But the occurrence periods of all kinds of *Monochamus alternatus* at different altitudes vary. For example, the occurrence periods of all kinds of *Monochamus alternatus* at an altitude of 400m is 30 days earlier than the time when they are at a higher altitude of 1200m. Enshi has a typical basin climate. The occurrence periods of *Monochamus alternatus* adults are significantly different, so the suitable periods of controlling them are also not the same. In this way, the study can provide the reliable base theoretically for controlling and forecasting *Monochamus alternatus* in Enshi.
