Abstract: This experiment was conducted in Altay Beitun region, locating in the valley basin area of the Irtysh River in Xinjiang, where mosquito occurs severely in the summer and endangers health of the local residents. This study identified two occurrence peaks of mosquito larvae, late May to early June and late June to early July and two peaks of mosquito adults, early to middle June and middle to late July. The major breeding sites of mosquito larvae were flooded meadows, drainage systems and flooded forest zones containing stagnant water. Aedes vexans was determined to be the dominant species in this region by morphological classification. The effectiveness of Bacillus thuringiensis subsp. israelensis (Bti) agent for control of A. vexans was tested. The LC₅₀ and LC₉₀ were 0.055 and 0.198 mg/L, respectively. Field test at sites with stagnant water and high density of mosquito larvae showed a mortality of above 96% after 48 h. With continuous use of the pesticide for three years (from 2011—2013), the number of adult mosquitoes in 2013 decreased more than 50% compared to that in 2011. These results will help control mosquitoes in Beitun town and in other regions in Xinjiang in the future.