Abstract: This study aims to elucidate the hydrodynamic regulation mechanisms of wheat straw mulching on rill flow dynamics, providing theoretical support for erosion control in straw-mulched sloping croplands.The indoor flume simulation scouring experiments was used to investigate the changes in hydrodynamic parameters of rill flow at different flow rates (3.0, 4.5, 6.0, 7.5, 9.0 L/min) and slopes (3°, 5°, 10°, 15°) with different amounts of straw mulch (0, 1.5, 2.5, 3.5, 4.5 t/hm2). The difference in flow regime between straw mulch and bare rill was significant (p <0.05); when the flow rate was ≤3 L/min, the flow pattern of rill was laminar, and when the flow rate was >3 L/min, the flow pattern was turbulent flow; The pattern of bare rills exhibited rapid flows, while those covered with straw transitioned to tranquil flow. When the flow rate was ≤3 L/min, the Reynolds number of the bare rill was less than that of the rill with straw mulch, and the Reynolds number varied with slope (3°, 5°, 10°, 15°). The Reynolds number decreased with the increase of slope; the Reynolds number of the straw-covered fine ditches increases with the increase of slope when the flow rate is >3 L/min. The Reynolds number was positively correlated with the slope and decreased with the increase of straw cover. The flow rate was positively correlated with the flow velocity and slope, and negatively correlated with the amount of straw. The flow index increased with the amount of straw mulching, and the relationship with slope was not significant. Straw mulching played an obvious role in increasing the resistance of rill flow, with the increase of straw amount, the Darcy-Weisbach friction factor and Reynolds number first showed a negative correlation, and then turned into a positive correlation after a certain amount of straw mulching was reached; the number of Froude was negatively correlated with the Darcy-Weisbach friction factor. Straw mulching can effectively slow down the flow velocity and increase the resistance coefficient, thus reducing the risk of fine rill erosion.