By analyzing the observed temperature from a small and a large louvered screen from March 2009 to February 2010, it is found that the mean monthly temperature and mean annual temperature from a small louvered screen are generally lower than those from a large louvered screen, but this difference is less, mostly less than 02 ℃. 〖JP2〗The mean maximum temperature has large differences in winter, with the maximum being 04 ℃. The difference of monthly extreme temperature is large and unstable, within ± 1 ℃. The differences of daily extreme temperature are more centralized, with the maximum temperature mainly distributed within -065 to 014 ℃, the minimum temperature within -04 to 002 ℃. The daily variation trends of temperature are about the same. The large louvered screen has faster heating speed and rapider reducing temperature at the stage of dramatic change. The difference is positive at cooling phase, and negative at heating stage; the maximum difference appears at 09:00 and 12:00 No matter under what cloud cover or wind velocity, the mean difference of air temperature in the two kinds of screens is almost within 02 ℃.