【Objective】The development of agriculture in the sloping uplands of red soil has been restricted by low water use efficiency, high temperatures and low fertilizer use efficiency．Interflow in the soil has been playing a important role in runoff generation, nutrient loss and soil erosion. Carrying soil nutrients along, it merges into rainfall-induced runoff, which flows into water bodies, thus causing environmental problems, like waterbody eutrophication．Nitrogen (N) as one of the common soil nutrients causing eutrophication is highly mobile in the soil because it is hardly absorbed and fixed by soil particles, so it moves easily with surface runoff and interflow as its main pathway of migration．Consequently, to study soil nitrogen loss related to the joint effect of surface runoff and interflow on slope lands is of great significance. In some regions, plentiful and concentrated rainfall results in surface runoff and interflow that enhances nutrient migration．Recently, researchers have studied patterns of nitrogen migration in red soil through surface flow and its impacting factors, as well as generation of interflows and its influence on nitrogen output．However, so far little has been reported on investigations that have taken into full account the joint effect of surface flow and interflow on nitrogen migration in red soil.【Method】In order to explore characteristics of nitrogen output in sloping uplands of red soil under natural rainfall, large-scale lysimeters were used in a field experiment carried out during the year from May 2015 to May 2016, on a sloping upland of quaternary red soil in Jiangxi, China. The experiment had three treatments, i.e. planted with grass, mulched with straw, and bare land laid out for observation of forms of nitrogen lost with surface flow and interflow (30, 60 and 105 cm) relative to treatment under natural rainfall.【Result】 Results show: (1) Interflow at 105 cm depth was an important channel of N loss on the slope of red soil where erosion wasn’t serious. The interflow in the soil layer 105 cm in depth contributed more than 71% of the total N loss while surface runoff and interflows in the soil layers 30 and 60 cm in depth did less than 23% and 6%, respectively; (2) N in the interflow was mainly in the form of dissolved N, composed principally of dissolved inorganic nitrogen (DIN), especially nitrate nitrogen. The proportion of DTN (dissolved total nitrogen) in TN was 54.8%~86.9% and that of DIN in DTN was 57.8%～97.1% in the interflow. The proportions of various forms of N in the surface runoff varied with the treatment; and (3) Grass coverage effectively reduced N runoff loss, while straw mulch increased the risk of N leaching loss. 【Conclusion】All these findings in the experiment provide certain scientific support to control of N runoff loss from red soil slopelands by establishing a suitable vegetation cover. The key to reduction of nitrogen loss from agricultural fields is to control the formation of interflow or subsurface runoff in sloping uplands of red soil slope and to reduce content of nitrate nitrogen in interflow.