Abstract: Based on ground meteorological and upper altitude data from 2009 to 2011 in Xining district, the characteristics of wind and thermal fields in atmospheric boundary layer was studied and simulated. The results show that, the surface wind field in Xining was complex, which had a great influence on terrain. The wind direction at higher frequencies agreed with valley's changes. The average wind speed in valley floor was lower, about 1 m·s^-1, and it had features of low wind speed in Beichuan Valley and Southwest Huangzhong County. The high and surface dominant wind direction was conversed below 100m, and the high dominant wind direction was mainly W and WNW at 7:00, however the dominant wind direction was mainly ESE and WNW, and the maximum wind speed was mainly W and WNW at 19:00. The vertical wind shear index is about 0.6 in winter, and about 0.45 in summer. The change of vertical speed in winter is greater than that in summer, and is greater during the nighttime in summer than during the daytime. The feature of thermal fields showed that the temperature inversion frequency is about 30% higher in winter than in summer. The characteristics of thermal fields were higher frequency and deeper inversion layer in the morning than in the evening. The characteristics of inversion in Xining district were more obvious than that in the valley city and humid region of Loess Plateau, weaker than that in the arid region of Loess Plateau. The characteristics of mixing layer height in winter and spring was higher, and the lowest in winter, while the mixing layer height in arid season is higher in humid season within the same temperature of air. The daily mean of mixing layer height has larger variation, from 200 to 3000 m, and larger daily variation of diffusive condition.