The Asian tiger mosquito, Aedes albopictus (Diptera: Culicidae), has a wide distribution in China with its northwestern limits among seven provinces. During 2006-2008, distribution information was collected in 33 urban and rural areas in those boundary provinces by collecting larvae or adult mosquito from different breeding sites. Additional information of seven sites was gathered from local health authorities. Three generally accepted climatic delineations affecting distribution of the species were studied for the northwestern distribution using a geographic information system software (ArcGIS). Climatic analysis showed that the annual mean temperature higher than 11°C, the mean temperature of the coldest month, January, higher than -5°C, and the annual precipitation above 500 mm covered almost all the confirmed areas and the seasonal expansion reached areas with nearly -10°C of the mean January temperature. As a main vector of dengue fever virus in a large part of China, where Aedes aegypti is absent, Ae. albopictus is also responsible for the risk for future epidemic of dengue fever and other viral diseases in China.