In order to understand the variation characteristics of potential evapotranspiration and influence factors in Guizhou province, Penman-Monteith formula, regression analysis, Mann-Kendall test analysis and GIS spatial analysis were used according to the conventional observation data of 80 meteorological observatories in Guizhou province from 1961 to 2015, and the potential evapotranspiration and its variation characteristics and influence factors in Guizhou province were calculated and analyzed.The results showed that the ET0 of Guizhou Province had a decreased trend in the past 55 years. The spatial distribution of the South was higher than the north, the West higher than the East, and it decreased from southwest to northeast. The mean temperature, maximum temperature and relative humidity were significantly correlated with ET0 except the mean wind speed.