Yield potential of nature. precipitation and effect of water and fertilizer for spring corn growth had been studied by means of field experiment and statistical analysis. Results show that the yield potential was 603. 6kg per mu and the potential coefficient was 1. O,which indicated that the water amount was enough to meet the requirement of the corn in abundant rain year,Improving soil fertility is the first measure to increase the spring corn yield and water efficiency at present. However ,increasing water supply will reduce water efficiency but not the yield.