Abstract: Field plot test was used to studied the effect of potassium fertilizer application on maize in sandy soil, the result showed that the maize yield was increased in sandy soil as the applying rate of potassium fertilizer was increased ，the optimal rate of potassium fertilizer was 225 kg K2O/hm2 at which the highest ratio of import to export with relative higher seed yield and potassium utilization efficiency can be got. Applying potassium fertilizer can improve the seed protein content too, but differing from the yield response to the applying rate of potassium fertilizer, the seed protein content reached highest point at the rate of 225kg K2O/hm2,then decreased as applying more rate of potassium fertilizer. Applying potassium fertilizer increased the soil available potassium content, for keep the balance of soil potassium fertility after the maize growth cycle, the applying rate of potassium fertilizer should reached 150kg K2O/hm2 . the maize seed yield showed significant positive correlation with the plant potassium content the coefficient was 0.87、0.95、0.94、0.99 at jointing stage, booting stage and heading stage respectively.