Using the daily maximum, minimum, and mean temperature data sets from 1975 to 2008 of six representative climate stations in Yunnan Province, the trends of extreme temperature are analyzed and the possible causes are discussed. The results show that the temperature trends of all representative climate stations were generally rising, while there was no systematic difference among them. Especially, the warming trends of Shangrila (representing the Plateau Climate) were distinct. The main features include: the warming rate of minimum temperature was the biggest; that of mean temperature was the next, and that of maximum temperature was the smallest. Meanwhile DTR (Diurnal Temperature Range) showed significant decreasing trend, which resembled the features of the Northern, Middle and Southern Subtropical Zones. However, the temperature in the temperate zone and the Northern tropical zone displayed different characteristics. As for the temperate zone, the maximum temperature increased significantly, and the growth rate of minimum temperature was slightly less than that of mean temperature, while DTR had no significant variation. With regard to the Northern tropical zone, the growth rate of mean temperature was the greatest, then the minimum temperature, and the maximum temperature the least, and there was no significant change in DTR. In addition, the statistical analysis of warm days, cold days, warm nights, cold nights, and frost days show that cold events were decreasing and warm events were increasing.