According to the result of simulated runoff experiment in laboratory, the dynamic movements of the mineral nitrogen's transport
by surface runoff and leaching are studied. Meanwhile, the Effective Depth of Interaction (EDI) of runoff with
soil mineral nitrogen is analyzed and confirmed. It is validated that the process of soil nitrogen loss by erosion is restricted by interaction of soil nitrogen with rainfall and runoff. There are much more soil mineral nitrogen loss by runoff than that by sediment. The concentration of soil mineral nitrogen loss in runoff wavelike changes, firstly achieving peak value, then gradually descending and increasing again after the rainfall ceased. Runoff and
rainfall intensity are considered as the important drivers for the mineral nitrogen's transport in surface runoff and leaching. The more the rainfall intensity is, the more the amount of soil nitrogen loss by erosion, the depth of peak value of soil NO~-_3-N concentration and the EDI. The observations of the temporal and spatial distribution of mineral nitrogen on the loess slope show, that there are different spatial distribution of the soil NO~-_3-N and the EDI, deepest in the middle and lower parts of the slope land, while shallower in the upper and bottom parts. It is proved that the infiltrating processes between soil NH~+_4-N and NO~-_3-N after the rainfall are distinct different.