Based on the observation data of average temperature, sunshine hours, wind speed, and relative humidity at 45 stations in Haihe Catchment during 1960—2012, we compared three potential evapotranspiration models with the Penman—Monteith model. The absolute and relative errors were used as the model evaluation indices. Hargreaves model based on energy balance proved to be the most suitable for potential evapotranspiration estimation in Haihe Catchment. The annual potential evapotranspiration declined at a mean rate of 2.04 mm?a-1 in 1960-2012. The inter-annual variations of potential evapotranspiration in the four seasons all showed a significant decreasing trend, with the largest decline in summer and the smallest decline in winter. Spatially, the average potential evapotranspiration during 1960-2012 tended to increase from the northwest part of the region to the southeast. Moreover, the decrease of potential evapotranspiration occurred in most part of the region, especially in the southeast, which means potential evapotranspiration may be mainly impacted by global dimming. However, potential evapotranspiration in the northwest part of the region showed an increasing trend, probably due to global warming.