Straw incorporation plays a vital role in regulating runoff and soil erosion of cropland. However, the benefits of straw incorporation to control runoff and soil erosion on croplands under different degradation degrees have not been fully clarified. This study was performed to investigate the benefits of straw incorporation to reduce runoff and soil erosion under different degradation degrees and determine its dominant influencing factors. The event runoff and soil erosion were measured from late May to late September 2022 using 16 runoff plots (9 m in length and 3.3 m in width) in the black soil region of Northeast China. The results showed that straw incorporation significantly reduced runoff and soil erosion on croplands with different degradation intensities. Compared to croplands without straw incorporation, runoff and soil erosion of straw incorporation decreased by 48. 8%, 40.0%, 30.9%, 25.5%, and 55.2%, 48.8%, 40.8%, and 36.5% for croplands of no, light, moderate, and strong degradation intensities, respectively. The roles of straw incorporation in controlling runoff and erosion decreased with rainfall intensity. Compared to light rainfall, runoff reduction ratio and erosion reduction ratio of moderate and heavy rainfalls reduced by 19.5%–61.3% and 27.5%–64.4%. The benefit of straw incorporation to control runoff and erosion was limited on strong degraded cropland or under heavy storm. Moreover, soil hydrological properties and crop growth characteristics decreased by land degradation and improved by straw incorporation, which inevitably affected runoff and soil erosion. Soil bulk density, maximum rainfall intensity of 30‐min, saturated water content, precipitation, rainfall intensity, saturated hydraulic conductivity, and total porosity were the dominant factors affecting the roles of straw incorporation in controlling runoff and erosion on degraded croplands. The results of this study are helpful to prevent land degradation or recover the functions of degraded lands in semi‐humid region. [ABSTRACT FROM AUTHOR]