Accurate simulation of the stalk-tool interaction during mechanized rapeseed harvesting is limited by the lack of accurate and reliable bonding parameters for discrete element stalk models. To address this issue, rapeseed stalks of the cultivar "Huayouza 62" at the optimal harvest stage were used. The intrinsic and contact parameters of the stalks were systematically determined through physical tests. A double-layer bonded model of the rapeseed stalk was developed in EDEM by using the Hertz - Mindlin with Bonding V2 contact model. Using the measured maximum bending failure force 43.02 N and maximum shear force 186.22 N as the dual response values, a Plackett - Burman design was firstly employed to identify significant factors, followed by a steepest ascent experiment to approach the optimal range, finally, a Box - Behnken design was used to optimize the solution. The results showed that the skin-skin normal stiffness per unit area X?, skin-core shear stiffness per unit area X?, and core-core normal stiffness per unit area X? had significant effects on the model. In the optimal parameter combination, X? was 6.80×10?N/m3, X? was 5.93×10?N/m3 and X? was 3.18×10?N/m3. Based on this combination, a double-layer bonded discrete element model of the rapeseed stalk was established. Simulations demonstrated that the relative errors between the simulated maximum bending failure force and maximum shear force and the measured averages were 2.11% and 2.39%, respectively. The mechanical behavior of the model was consistent with that of actual stalks. The research result can provide a reference for the discrete element modeling of rapeseed plants and the design of harvesting machinery.