Abstract: Flax stems are fiber-abundant and possess high nutritional value in their seeds, making them an essential oilseed and cash crop in the northern and northwestern hilly regions of China. Currently, domestic mechanized harvesting of flax primarily relies on segmented harvesting, complemented by combined harvesting. However, the issue of flax stem entanglement during the combined harvesting process has emerged as a significant bottleneck, severely impacting harvesting efficiency and industrial development. Because of the high cellulose content of flax stems, strong toughness, intertwining capsules and fruits during maturity, and the limited power and space layout of combined harvester models in hilly areas, which leads to the stems being easily entangled in the conveyor churn during harvesting and poor mobility and other phenomena, this study investigates the influence of the key components of the header of the common grain combine harvester (T₁ model) on the motion attitude of the flax plant by constructing a discrete element flexible model of the flax plant using MBD-DEM co-simulation technology, analyses the reasons for the tangling of the header of the common combine harvester, puts forward a device for solving the tangling of the header in order, then further elucidates the mechanism of the anti-entanglement mechanism of the flax header through the optimization of the anti-entanglement key components of the header (T₂ model) on the motion attitude of the flax plant, and finally carries out a field verification test. The MBD-DEM co-simulation results indicate that: before 0.6 seconds, the average X-axis velocity of the flax plant of T₁ model exhibits greater variation compared to the T₁ model itself. The average X-axis velocity changes minimally across different segments until 0.6 to 0.85 seconds, when the flax segments enter a phase of high-speed movement. After 0.85 seconds, the flax segments transition into a relatively stable movement phase, during which the plants accumulate at the spiral blade, accompanied by their rotational motion and the propulsion provided by the spiral blade, leading to entanglement. Before 0.45 seconds, the Z-axis velocity changes of the flax plant segments in the T₁ model are minimal, but after 0.45 seconds, these velocities begin to change significantly, albeit within a narrow range. In the T₂ model, from 0.64 to 0.77 seconds, the X-axis velocity changes of the flax plant segments accelerate, and from 0.77 to 1.5 seconds, the flax segments experience high-speed movement. The addition of an anti-entanglement plate results in more pronounced X-axis velocity changes. Before 0.55 seconds, the Z-axis velocity changes of the flax plant segments in the T₂ model are minimal, but after 0.55 seconds, these velocities begin to change significantly. Field verification results demonstrate that: the T₁ model has a total loss rate of 3.32%, an impurity rate of 3.57%, four instances of winding, and an efficiency of 0.14 hm²/h; the T₂ model has a total loss rate of 2.29%, an impurity rate of 3.39%, no instances of winding, and an efficiency of 0.23 hm²/h, representing a 39.13% improvement in operational efficiency over the T₁ model. The T₂ model’s operational performance meets the standards required for flax harvesting, providing valuable insights for the design and testing of flax combine harvesters.