Based on the daily climatic data from 204 meteorological stations within the Huang-Huai-Hai River Basin and its surrounding areas from 1961 to 2010, the potential evapotranspiration in the aridity index is calculated, and then on the basis of this, the aridity index and the climate division of the basin are created with the Kriging interpolation method,meanwhile the spatial-temporal evolution characteristics of the aridity index based climate division of the region for the recent 50 years are analyzed as well. The study result shows that (1) since 1961, the aridity index in the Huang-Huai-Hai River Basin shows an increasing trend with a slow fluctuation,but the increasing amplitude is less, while the average aridity index is 2. 46 with a significant mutation around 1998; (2)based on the aridity index, the Huang-Huai-Hai River Basin is divided into four climatic zones, i. e. humid,sub-humid, arid and semi-arid, while a gradually increasing trend of the arid-humid difference is there between the semi-arid zones and the other arid-humid zones for the recent 50 years ; (3) in view of the spatial scale, the general characteristics of the aridity index of the whole basin is large in north and less in south with a gradually decreasing trend from north to south.