Abstract: The influences of nitrogen and phosphorus nutrients on seed yield and quality of maize were studied by using a split plot experiment in the rainfed lands of the Loess Plateau. The results show that crude protein, crude fat, lysine contents, seed bulk density, yield and water use efficiency (WUE) are increased with the application of nitrogen and phosphorus fertilizers, especially for the nitrogen fertilization, while crude starch content of maize seeds are decreased. The contents of soil alkalized-N and available P are also increased with the fertilizer application, which are useful for the nutrients’ uptake, root growth and biomass accumulation. The abilities of absorbing and transforming N and P nutrients in stalks and leaves are increased, and the nutrients’ transportation to spike axises and seeds are improved. The density of seed milking is significantly increased, which could enhance the accumulations of N and P in seeds, grain weight and grain quality during the middle and late milking period of maize.