The efficiency of applied Potassium fertilizer and the reasonable amount of applied Potassium fertilizer on summer maize of high yield alluvial soil of Henan was studied by field trial. The results showed，that applied Potassium fertilizer can decrease the ear height and improve the plant height, ear length, hundred grains weight to enhance the ability of the maize resisting stress and improve the properties of yield structure, and maize yield increased with the increasing amount of applied Potassium fertilizer. But the yield of the high potassium treatment become slower, its economic profit is lower. The amount of potassium constructed of 150kg/hm2 is comparatively reasonable on the high fertility alluvial soil soil.