Abstract: 30 years locatal experiment was conducted to study the effects of longterm fertilization on nitrogen metabolism of summer maize and the results showed: with the increase of fertilization amount, nitrogen metabolism was more exuberant, NR activity in spike leaf was higher after silking, the treatment of M2N2 can improve NR activity remarkably, which is increased by 4.0% more than the control. M2N1、N2PK、M1N2 then followed ,They are increased 3.7%、3.4% and 3.1% separately. the change tendency of free amino acid and soluble protein content was similar with NR activity. the treatment of M2N2 increased free amino acid and soluble protein content by 19.6% and 22.2% as compared with the control significantly. M2N1、N2PK and M1N2 then followed. free amino acid content are increased 17.9%、16.7%、and 15.4% separately. While soluble protein content are increased 18.5%、18.4% and 17.9% separately. Under the condition of used organic fertilizer with some inorganic nitrogen, NR activity in spike leaf kept longer time with higher value at filling stage, and soluble protein content in spike leaf was also higher. The treatment of combined application inorganic nitrogen, phosphorus, Potassium was much better than the treatment of combined application of inorganic nitrogen and phosphorus or the treatment of combined application of inorganic nitrogen and Potassium in NR activity in spike leaf、soluble protein content in spike leaf.