The experiment was arranged to apply a large scal of N-fertilizer mixed with proper P-fertilizer. The productive potentiality and effect of a small amount of N-fertilizer applied to springcorn were analysed.It was showed that the tuning point of corn yield was not clear when N-fer-tilizer applied reached to 570kg/hm². Simulating N-fertilizer effect curve with the equation Y=A+Bx+Cx²,the amount of fertilizer applied correspond ing to the biggest yield was about403kg/hm² in general years. The interrelation was more clear when simulated with equation of Y=A+Blnx or y=A·x^B,but it did not own the maximum point of production. It indicatesthat the productive potentiality of N-fertilizer to spring corn is very high.To apply very smallamount of N-fertilizer,it not only can improve yield and achieve economic benefits clearly,butalso can improve protein content in corn seed.The effect curve of N-fertilizer and yield is differ-ent with the traditional ideas at section of small amount of fertilizer applied