[Objective] The effects of slope length on the runoff and sediment yield of the engineering accumulating body were studied in order to provide theoretical basis and technical support for the reasonable prevention and control of soil and water loss in engineering accumulations in production practice.[Methods] Three slope (24°, 28 °, 32 °) and five slope length (4,8,12,16,20 m) were selected for simulated field test of runoff erosion on exposed engineering accumulating body.[Results] The runoff rate and sediment yield of 24°, 28° and 32° slopes fluctuated with the increase of slope length. The correlation between the runoff rate and the sediment yield of the 4 m and 8 m slopes was significant, the correlation between the runoff rate and the sediment yield of the slope at 12, 16 and 20 m was only significant at 32°. Cumulative flow rate and cumulative sediment yield had a power function relationship with slope length. The cumulative sediment yield and cumulative yield had a linear function relationship.[Conclusion] The influence of slope length on slope runoff rate and sediment yield was different due to different slope; cumulative runoff and sediment yield increased with slope length.