The unsaturated zone is the link which water and nutrient transforms between atmosphere and aquifer, and it is crucial to study the distribution and accumulation of NO₃^--N for preventing nitrate pollution in groundwater because it is the place where farmland nitrate distribute and accumulate and is the channel that nitrate leaches to the aquifer. In this study, the Geoprobe direct push system was employed to obtain 10.5 meters of continuous soil core samples from the typical deep unsaturated zones in croplands under two different fertilization(N0, no nitrogen fertilizer applied; and N600, 600 kg/(hm²·a) nitrogen fertilizer applied in North China Plain in order to analyze the profile distribution, accumulation and key influential factors of NO₃^--N in soils. The results showed that NO₃^--N remained stable in N0, however, in a long-term application of 600 kg/(hm²·a) nitrogen fertilizer (N600), NO₃^--N leached to 10.5 m and accumulated in the deep unsaturated zone, the peak of accumulation was determined by soil texture and moisture content. The distribution and accumulation of NO₃^--N were mainly affected by water migration, soil texture and denitrification.