In order to study the effects of slope gradient on sediment yield by ephemeral gully erosion on slope surface, taking the ephemeral gullies on the hilly and gully slopes of the Loess Plateau as the research object, four slope gradients including 14.0°, 18.5°, 26.0° and 29.0°, and five discharge flows of 5, 10, 15, 20, 25 L/min, were selected to study the effects of slope gradients on runoff rate, sediment yield rate, sediment concentration and total runoff and total sediment yield. The results showed that the slope gradients were positively correlated with runoff rate and total runoff at 5, 10, 15, 20, 25 L/min, and the runoff rate and total runoff increased with the increase of slope. Under the different discharge flows and gradients, the sediment yield rate, sediment concentration and total sediment yield had the same trend over time:increasing first-reaching maximum-decreasing fluctuatingly-stabilizing finally. The relationship between sediment yield rate, sediment concentration, total sediment yield and slope gradient:sediment yield rate, sediment concentration and total sediment yield increased first and then decreased with the increasing slope gradients, and the maximum value appeared at 26.0°. The sediment yield rate, sediment concentration and total sediment yield at 26.0° were 1.06~2.87 times, 1.31~2.21 times and 1.08~2.77 times of those at 14.0°, respectively. There were critical gradients for sediment yield rate, sediment concentration and total sediment yield, which ranged from 18.5° to 29.0°.