Abstract: Based on the daily temperature, precipitation, wind speed, sunshine hours, total solar radiation and related humidity data of the 108 meteorological stations in southwest China during 1960 to 2013, the authors used the methods of Penman-Monteith model and inverse distance weighted interpolation, to analyze the temporal-spatial variations and the possible influential factors of the reference crop evapotranspiration (ET₀) in this region. The results were as follows: (1) the annual mean value of ET₀ was decreasing in fluctuation and the decreasing rate was -4.509 mm/10 a in recent 54 years, ET₀ had the most significant reduction in 1990s and the most increase of 12.744 mm in 1970s; from late 1970s to the beginning of the 21^st centuries, ET₀ decreased significantly; (2) on the seasonal scale, the change trend of ET₀ decreased in spring and summer, but increased in autumn and winter; (3) the change trend of the reference crop evapotranspiration had obvious differences in the space, there was an obviously high value center in Yunnan-Guizhou Plateau and it decreased gradually in the surrounding area; the distribution area of low value was far greater than that of high value, the high value area was located in the Yunnan Plateau-Guangxi Basin and the low value was distributed in Sichuan Basin, Guizhou Plateau, Songpan Plateau and the high altitude area in northwest Yunnan; (4) influencing factors of reference crop evapotranspiration were mainly sunshine hours, wind speed and relative humidity in southwest region, but the main control factor was not the same in all regions.