With the fast urbanization of China, the existence of obstacles around the meteorological sites makes observational data lose representativeness, accuracy and comparability. In order to study how obstacles affect wind fields quantitatively, an observational experiment of a building is carried out in Guyuan, Hebei Province. The influence of obstacles on wind speed and wind direction is analyzed by comparing the wind data before and after the completion of the building. The analysis of the experiment results shows: (1) Obstacles can weaken wind speed, which is related to the background wind speed, the greater the wind speed the more obvious the attenuation. (2) While the wind velocity is between 2 m/s and 6 m/s, the wind speed attenuation of the lee sites decreases with the increasing of distance behind the obstacle, with the attenuation rate of wind speed being 15 percent or so at the distance of 10 times as long as the height of the obstacle; when the background wind velocity is more than 6 m/s, the wind speed attenuation of the lee sides weakens firstly and then strengthens, with the maximum attenuation at the distance of 5 times as long as the height of the obstacle, and the velocity attenuation by about 20 to 30 percent at the distance of 10 times as long as the height of the obstacle. (3) The frequency of prevailing wind direction decreases because of the obstacle, and the influence distance is 6 times as long as the height of the obstacle.