To address challenges associated with inconsistent lodging degree and the irregular corm size during the harvest of tumorous stem mustard, which is difficult to determine the optimal harvesting forces, a specialized combine harvester was designed based on the special growth traits of this crop. An innovative harvesting methodology, involving initial pulling followed by root cutting, was adopted, and the dynamic simulation analysis of the key pulling device was carried out. Based on the analysis of the harvest process of mustard tuber and its stress state, the interaction force between the V-shaped cone roller of the extraction device and the mustard tuber was studied in detail. Static friction, elastic restoring force, and dynamic friction force at different stages of the plucking process were mathematically derived, so as to establish the dynamic model for corm extraction. To comprehensively analyze the interaction between the extraction device and the mustard tuber, and further optimize the key parameters of the device, a three-dimensional model of the mechanism was established using SolidWorks, subsequently simplified and imported into ADAMS software for dynamic simulation. Considering the application points and magnitudes of forces experienced by the mustard corm during extraction, a bushing force element was employed in simulate to represent the flexible connection between the tuber (modeled as a non-rigid body) and its root. This approach enabled the construction of a rigid-flexible coupling model representing the interaction between the mustard and the combine harvester's pulling device. Taking the pull-out force as the primary performance metric, the performance simulation tests of the pull-out process were carried out by selecting the opening spacing of the pull-out roll, the rotation speed of the pull-out roll and the driving speed as the test factors. The influence of different operating parameters on the pull-out force exerted by the pull-out device was elucidated. Analysis of the simulation results indicated no obvious linear relationship between the opening spacing of the pulling roller, the rotation speed and the extraction force. Furthermore, the stability of the extraction force was observed to decreases with the increases in both the opening spacing and the driving speed of the machine. The working efficiency of the extraction device decreases with an increase in opening spacing, and was found to be largely independent of the pulling rollers' rotational speed. The range analysis of the test results identified the optimal working parameter combination of the extraction device as: the opening spacing of the extraction roller 45 mm, the rotation speed of the extraction roller 120 r/min, and the driving speed 1.0 km/h. Under these conditions, the extraction force was the largest, the maximum value 487.2 N. The research results provide theoretical support for the design and optimization of the mustard combine harvester.