In order to investigate the response characteristics of the runoff and organic carbon loss to slope gradients in slope purple soil farmland with contour ridges, the surface runoff, interflow and dissolved organic carbon loss were studied during maize growth stages. Runoff plots and field artificial rainfall simulation methods were adopted. The results showed that the surface runoff displayed an order of 20° > 15° > 10° during the whole maize growth stage, while the interflow for 10° > 15° > 20°. For the different slope gradients, the surface runoff displayed an order of seedling stage > mature stage > jointing stage > tasseling stage, however, the interflow followed:tasseling stage > jointing stage > mature stage > seedling stage. The dissolved organic carbon (DOC) mass concentrations of surface runoff showed 20° > 15° > 10° during the whole maize growth stage, and seedling stage > jointing stage > mature stage > tasseling stage for the different slope gradients. The DOC mass concentrations of interflow showed an order of 10° > 15° > 20° at seedling stage, jointing stage and mature stage. The DOC mass concentration of interflow at seedling stage was maximum and tasseling stage was minimum for the different slope gradients. The DOC migration flux of surface runoff displayed an order of 20° > 15° > 10° during the whole maize growth stage, and seedling stage > mature stage > jointing stage > tasseling stage for the different slope gradients. The DOC migration flux of interflow displayed an order of 10° > 15° > 20° during the whole maize growth stage, while DOC migration flux of interflow for the different slope gradients showed the consistency with surface runoff. These results could provide theoretical basis for runoff and organic carbon loss regulation under different slope gradients during maize growth season.