Utilization of maize straw in agricultural fields can impact soil characteristics and rill erosion resistance, and the underlying mechanisms and temporal patterns of these changes remain inadequately understood. The aim of this study was to investigate the effects of ground maize straw returning on the erosion resistance of sandy loam soil. A L9 (33) orthogonal table was used to evaluate three factors: straw length, mixing depth, and returning amount. Soil critical shear stress (tau c) and rill erodibility (Kd) were measured three times using submerged jet erosion test equipment at 7, 9, and 12 months after incorporating the maize straw. The results showed that rill erosion resistance was initially influenced by soil porosity, water content, and humus fraction in the early stage after straw return, but later by soil humus fraction, organic matter, water content, and the mechanical action of the straw. Macroscopic inter-aggregate pores controlled tau c, while microscopic intra-aggregate particle attractions controlled Kd. As the decomposition time of the straw increased, tau c first increased and then decreased, while Kd decreased and then increased. Straw length, mixing depth, and returning amount had a greater effect on Kd than on tau c, with contributions ranging from 81% to 93% of the variation in Kd. These findings could serve as a reference for simulating and controlling the effects of soil erosion on sloping croplands by optimizing the conditions for incorporating straw.