Abstract: The maximum and minimum temperature data of three stations in Xining (city), Huangzhong (southern suburb) and Huzhu (northern suburb) from 1986 to 2015 were selected to study the Xining heat island effect based on the Diurnal Temperature Range (DTR). The results show that the annual average DTR of urban and northern suburbs have been on the decline for the past 30 years, decreasing by 0.15 and 0.29 ℃/10a. The 21st century 10 years, The urban area was relatively low level of up to 0.73 ℃. DTR had a weekend effect. Urban DTR declined faster than the suburbs. The trend of the DTR was positive in spring and negative in the rest of the year, especially in urban areas in winter, decreasing by -0.76, which was much larger than the suburbs. Urban DTR gradually reduced, indicating that the degree of urban turbidity increased year by year, Urban Heat Island increased.