Longterm field experiment was carried out from 2009 to 2013 to study the effect of different fertilization treatments on yield and active oxygen metabolism of summer maize.The results showed that,in NPK treatment the yield of summer maize significantly increased,which was up to 9 299.85 kg/hm2 and grains per spike and 1 000 grain weight were the highest.The spike length and spike weight of NP treatment had no significant difference with those of NPK treatment.Nitrogen effectively improved the chlorophyll content of spike leaf and grain filling rate and it had the most influence on the activity of peroxidase of maize leaves located near the ear.N and K fertilizer effectively increased the superoxide dismutase activity and soluble protein content of maize leaves located near the ear,and decreased their content of malondialdehyde.Therefore,the rational combination of N and K could effectively improve the efficiency of photosynthesis,delay leaf senescence and increase the grain yield of maize.