Abstract: An eight-year long-term experiment in Loess Plateau Area demonstrated the importance of balanced fertilization. In a rotation of wheat-corn, when nitrogen application rate was as high as 352kghm-2 a-1, NO3--N accumulation in a 4 meter deep profile was more than 1000kg/hm2 if there was no application of phosphorus fertilizer(treatment of N and NK), and 50%～60% of it distributed below 2 meter soil layer. For treatment of applying phosphorus fertilizer(NP), the NO3--N accumulation was only about 220kg/hm2, and more than 80% of it distributed in a layer of 0～2m. Balanced fertilization can greatly decrease soil NO3--N accumulation by increasing soil water use efficiency and nitrogen uptake.