Based on daily meteorological data from 21 meteorological stations in Liaoning Province from 1965 to 2017, Penman-Monteith method, wavelet analysis method, sensitivity coefficient and factor analysis method were used to explore the spatiotemporal variation of potential evapotranspiration and the quantitative analysis of its main meteorological elements. The results show that: (1) from the perspective of the temporal change, the potential evapotranspiration in Liaoning Province has a significant downward trend, with a change rate of 2.89 mm/a and a multi-year average of 955.82 mm. The potential evapotranspiration of the 20 meteorological station has been decreasing, but that of one meteorological station has been increasing. On the spatial scale, the potential evapotranspiration of Liaoning Province decreased from west to east. (2) The potential evapotranspiration is most sensitive to relative humidity and least sensitive to minimum temperature. (3) The average wind speed is the meteorological factor that has the greatest influence on the potential evapotranspiration, and the relative humidity has a negative correlation with the potential evapotranspiration.