Abstract: Spinach production in China constitutes over 90% of global output, with root-cutting into the soil being the sole harvesting method that satisfies national consumption needs. The complexity inherent in analyzing the interaction between spinach roots, soil, and cutting implements during the harvesting process had prompted a reevaluation of existing models. Current root-soil complex models inadequately accounted for the influence of fibrous roots on the mechanical properties involved in root cutting, leading to imprecise calibration parameters. This study presented a discrete element model that simulated the actual growth conditions of spinach, establishing a comparative framework for analyzing scenarios both with and without fibrous root representations. By statistically analyzing the external dimensions of spinach taproots and the growth angles and distribution characteristics of fibrous roots in the soil matrix, a complete model including taproots and fibrous roots and the corresponding soil model was established using the discrete element method. A series of tests including taproot accumulation, shear testing of the taproot, tensile testing of fibrous roots, and soil accumulation assessments were conducted to calibrate the intrinsic, contact, and model parameters governing interactions between spinach roots and the soil medium. Calibration results demonstrated that the relative errors for the simulation outcomes of the taproot repose angle and ultimate shear force compared to measured averages were 0.23% and 0.98% respectively. Similarly, the relative error for the ultimate tensile force of fibrous roots was recorded at 0.9%, while the soil repose angle exhibited a relative error of 0.18%.Utilizing the calibrated parameters, we established a discrete element model of the spinach root-soil complex and conducted a validation test for the ultimate shear force within this complex. Single-factor testing revealed that, within the specified range of factor values, the ultimate shear force escalated with increases in the static friction coefficient and the bond radius coefficient between the root and soil. Conversely, it exhibited an initial increase followed by a decrease in response to rising values of the rolling friction coefficient, normal stiffness per unit area of the bond, critical normal stress, and the contact radius coefficient of soil particles. Notably, the shear stiffness per unit area of the bond between roots and soil particles had negligible influence on the ultimate shear force, while critical tangential stress exerted a minimal but non-negligible effect. Results from the Box-Behnken response surface optimization tests indicated that the significance of factors influencing ultimate shear force, ranked from most to least significant, was as follows: critical normal stress of the bond, static friction coefficient between spinach roots and soil, bond radius coefficient, rolling friction coefficient between roots and soil, soil particle contact radius coefficient, and bond unit area normal stiffness. The relative error between the optimized ultimate shear force and measured values was recorded at 0.44%, corroborating the accuracy and reliability of the developed spinach root-soil complex model. This model effectively captures the mechanical characteristics pertinent to the root cutting process during spinach harvesting. The comparative analysis of root cutting characteristics—contrasting scenarios with and without fibrous roots—revealed that the ultimate shear force of the root-soil complex lacking fibrous roots was approximately 11.4% lower than that of the complex inclusive of fibrous roots. Moreover, the relative displacement between the main root and the soil increased by roughly 60.3%, which shows the fibrous roots have the obvious role of binding the soil and stabilizing the taproot. These findings underscore the enhanced simulation accuracy afforded by a comprehensive spinach root system model, facilitating advanced analysis of the interaction dynamics among spinach roots, soil, and cutting tools.