The study on the effects of N application rate on the N utilization, yield and quality of mono- and inter-cropped spring- and summer-sown maize showed that under both of the cropping systems, the N uptake, grain yield, dry matter accumulation, and grain protein yield of spring- and summer-sown maize were increased with increasing N application rate. Due to the same demand of N nutrition, there was a competition between spring- and summersown maize in inter-cropping system, especially under low level N application. Spring-sown maize was of superiority in inter-cropping system, but its N uptake was still less than that in mono-cropping system. The competition could be offset by increasing N application. When N application increased from 187.5 kg x hm(-2) to 375 kg x hm(-2), the average increment of dry matter yield of mono-cropped spring- and summer-sown maize was 1.717 kg x kg(-1) N, while that of inter-cropped spring- and summer-sown maize was 12.179 kg x kg(-1) N. The average increment of protein yield of mono- and inter-cropped spring- and summer-sown maize was 0.305 kg x kg(-1) N and 1.829 kg x kg(-1) N, respectively, with the land equivalent ratio increased from 1.59 to 1.91. Compared with mono-cropping, inter-cropping spring- and summer-sown maize could get higher yield and higher quality, and this effect was increased with increasing N application rate.