The influence to the city climate is researched quantitatively through the meteorological log in recent 70 years by the method of comparison between the urban and the suburban's. And the principle components (high, low temperature components) of air temperature are extracted by the method of the principle component analysis. The influence of the urbanization to the city air temperature in Lanzhou is analyzed quantitatively. Certainly, the cause of the air temperature change is not only by the influence of human but also by the change of the more large-scale climatic background. So, before analyzing the change of the city climate, the trend of the large-scale area climate by T-test is discussed and the variation of the region climate has the characteristic of 11-years cycle is obtained.