Meteorological datasets from 105 meteorological stations in Xinjiang were utilized to analyze the characteristics of extreme maximum air temperature in the summer of 2015. The extreme maximum air temperature more than 35 ℃ firstly occurred in early July in southeastern and eastern Xinjiang region,and then spread westwards and northwestwards in mid-July. In the late July,the range of extreme maximum air temperature reached up to the top,both in northern and southern Xinjiang regions. The extreme maximum air temperature mainly occurred in late July in 89 meteorological stations,accounting for 84.8% of total meteorological stations. There were 55 meteorological stations,accounting for 52. 4%,had the longest durations of maximum air temperature, ranked first in the historic record. There were 23 meteorological stations,accounting for 21. 9%,had the extreme maximum air temperature ranked first in the historic record. An extreme maximum air temperature, 47. 7 ℃,took place in Turpan. This extreme maximum air temperature resulted in summer average air temperatures in eight meteorological stations ranked first in the historic record. Average air temperature in July ranked first in the historic record in southern Xinjiang region and the Tianshan Mountains,and average air temperature in July exceeded the highest records in 57 meteorological stations,accounting for 54. 3%. During air temperature rising process,0 ℃ level height in July reached up to the top since 1991. For example,0 ℃ level over the Kaidu River basin of the Tianshan Mountains had higher than the value averaged from 1991 through 2015 for 33 days. High-pressure ridge in 500 hPa level over the Iranian Plateau moved eastwards was the direct cause of extreme maximum temperature occurred in Xinjiang in July. The form,center location and intensity of the high pressure at 100 hPa level height in Southern Asia also reflected the evolution of high air temperature in summer of 2015 in Xinjiang. The high air temperature resulted in quick melting of snow and glaciers,causing snow and ice melt flood in the Tarim River basin in 2015.