[Objective] The scouring of cross-ridge slope land in the Manchuan-Manggang black soil area was studied, in order to provide a theoretical basis for black land conservation.[Methods] Field scouring experiments were performed on runoff plots in 10, 30, 50, and 70 m sloping farmland with ridge farming, to investigate the processes of runoff and sediment production with different volumes of upslope inflow.[Results] Under the three scouring flow rates of 0.34, 0.67, and 1.00 L/min, the runoff coefficients and sediment contents fluctuated continuously with increasing slope length, but they stabilized at different magnitudes and times at different scouring flow rates. The cumulative runoff production and cumulative sediment production both increased with increasing scouring flow rate, but the maximum values of both occurred at different slope lengths under the same scouring flow rate. When the scouring flow rate was 0.34 L/min, there was a significant correlation between the runoff coefficient and sediment content for the four slope lengths (10, 30, 50, and 70 m). The cumulative sediment production increased with the increase of the cumulative flow rate, with shorter slope lengths exhibiting a stronger linear relationship. When the scouring flow rate was 0.34 L/min, the ranking of the different slope lengths by the amount of soil erosion was 30 m> 10 m > 70 m > 50 m. At scouring flow rates of 0.67 and 1.00 L/min, the order was 30 m > 50 m > 70 m > 10 m. Under the scouring flow rate of 1.00 L/min, the erosion of the 30 m slope was 4.2 times the erosion of the 10 m slope.[Conclusion] Slope erosion increases with increase of scouring flow rate; However, 30 m is the critical slope length for erosion of cross-ridge slope land, and rill development is the main source of soil erosion on cross-ridge slope land.