To further understand wind fields in mountains and hilly areas in the north-south climate transition zone, based on the March 2015 to February 2016 observational data of ST (stratosphere-troposphere) wind profiler radar, the variation characteristics, and vertical structure of 20-km high wind fields in Huainan were analyzed. The results show the following: In Huaihe River valley, the wind field exhibited significant vertical changes at 850 hPa, 700 hPa, 500 hPa, and 100 hPa; through the seasons, the wind speed and its amplitude first decreased and then increased; they were minimum in summer, followed by in autumn, and maximum in winter, whereby the seasonal variation amplified with increasing height. The vertical distribution of the wind field displayed a great difference; the speed was mainly less than 10 m/s, and the wind directions below the middle and lower levels shifted; western winds of 10-25 m/s dominated the region above these levels. As observed from the annual wind vertical structure, in the lower level, mainly about 5 m/s southern wind turned to the west with less than 10 m/s at 2 km height; 15 m/s western wind was developed at 5 km height; its speed continued to increase and reached 25 m/s at 10 km height; when turning north from 15 km height , it gradually decreases to a level closer to that of the lower wind field until about 20 km.