In order to study the variation of runoff and sediment yield and gully erosion characteristics on alien soil slopes with different slope lengths in the abandoned mining area of Wula mountain, scouring tests were conducted by designing field runoff plots with different slope lengths (2, 4, 6, 8 and 10 m) under two slope gradients (15° and 20°). The results showed that: (1) The variation range of initial runoff generation time and runoff generation stop time both increased with the increasing of slope length. The runoff rate increased rapidly at the beginning and fluctuated irregularly after reaching the initial peak value. The cumulative runoff increased with the increasing of slope length. The runoff rate and cumulative runoff were highly significant (p＜0.01) correlated with slope length and runoff generation time and their interaction, and cumulative runoff showed a power function correlation with slope length and runoff generation time under the two slope gradients. (2) The sediment rate increased rapidly at the beginning and reached the initial peak value, then decreased gradually with the increasing of scouring time, and its mean value increased with the increasing of slope length, and the total cumulative sediment yield increased with the increasing of slope length. The cumulative sediment yield was significantly correlated with slope length, runoff generation time and their interaction (p＜0.01), and the cumulative sediment yield was related to the slope length and runoff generation time as a power function under the two slope gradients. (3) The average cross-sectional area of erosion ditch from the top showed two trends of decreasing along the slope and decreasing-increasing-decreasing again. The cumulative sediment yield and the estimated gully erosion volume had a highly significant correlation(p<0.01), and their difference increased with the slope length, and their ratio tended to increase firstly and then decrease with the increasing of slope length, and the maximum value appeared at 6 m slope length. The research results could provide technical support for erosion control and erosion model establishment of alien soil slopes in mine rehabilitation.