Potential evapotranspiration(ET_0) is an important metric in measuring drought conditions for an area. Examining ET_0 changes is critical for estimating crop water demand, and thus it is crucial for improving water use efficiency in the context of global warming. Based on daily meteorological data of 151 meteorological stations in Sichuan province from 1961 to 2014, the authors calculated ET_0 with the Penman-Monteith formula for the three terrain regions of Sichuan: Sichuan basin, Panxi region and Western Sichuan Plateau, and also analyzed relative variation and sensitivity coefficients of the major meteorological factors (i.e., mean air temperature, relative humidity, radiation hours, and mean wind speed), and the spatiotemporal changes in their contribution to ET_0 changes. The results showed that ET_0 in the Sichuan basin and the Western Sichuan Plateau presented a weak declining trend, as opposed to an increasing trend in Panxi region. In terms of spatial distribution, ET_0 was high in the Panxi region and the Western Sichuan Plateau (1000-1350mm·y-1), and it was low in the southwestern Sichuan Plateau (651-900mm·y-1), with a decreasing and then increasing gradient of ET_0 from the southwest to northeast. The effect of each meteorological factor on ET_0(i.e., contribution of each meteorological factor to ET_0 change) was determined by their sensitivity to ET_0 and relative variation. ET_0 was most sensitive to relative humidity across the three regions, with sensitivity coefficients of-1.13,-1.40,-1.53, respectively. Among all the meteorological factors, the variable with the highest long-term relative variation was mean wind speed in Sichuan basin (-29.7%) and Panxi region (-16.3%), in contrast to mean air temperature in Western Sichuan Plateau (40.4%). Further analyses suggested that the dominant factor determining ET_0 for Sichuan basin and Western Sichuan Plateau was mean wind speed, and that for Panxi region was relative humidity.