To address the difficulty in revealing the abrasion mechanisms due to the unknown flow pattern of the rice straw transported by the spiral churn of the cutting table, this study investigated the conveying process of rice straw by the combine harvester header auger during harvesting. The behavior of rice straw contact units was analyzed, and a mathematical model of flow velocity was established to plot the trajectory of the straw’s centroid. Discrete element method simulations were employed to model the conveying process, obtaining the centroid trajectory. The wear profile of the header was measured and compared with the theoretical and simulated straw trajectories. The results showed that when the friction coefficient decreased from 0.3 to 0.1, the axial velocity of rice straw driven by the outer edge of the spiral blades increased from 1 058.83 mm/s to 1 123.59 mm/s, while the circumferential velocity decreased from 670.59 mm/s to 439.40 mm/s. The simulated straw trajectory closely matches the theoretical model, with a mean square error of 0.386 7-6.188 3. However, the wear profile aligned well with the theoretical trajectory only when the axial displacement of rice straw and spiral blade contact ranged from 0 to 64 mm, with an overall MSE of 29.637 6.