In order to solve the problem that rapeseed grains are easily broken in the process of shredding and throwing in a self-developed rapeseed combine, the discrete element simulation of kernel crushing and the optimization of the shredding and throwing device were carried out. Based on the discrete element method, the rapeseed kernel bonding model was constructed and uniaxial compression test was carried out. According to the steepest climb test and Box-Behnken test, the optimal parameter combination of rape kernel bonding model is 7.0×109N/m, 6.82×109N/m, 6.61×1010Pa, 8.18×1010Pa, when the normal stiffness coefficient, tangential stiffness coefficient, critical normal stress and critical tangential stress are respectively. The simulation value of rapeseed grain crushing load was 12.67N, and the relative error with the physical value was 3.59%. Combined with the rapeseed grain bonding model, a simulation model of the shredding and throwing device of the rapeseed combine harvester was established. The three-factor and three-level Box-Behnken test was carried out with the rotating speed of the drum, the shredding clearance and the number of cutters as test factors, and the optimal parameter combination of the shredding and throwing device was determined. The results showed that: The optimal parameter combination of the shredding and throwing device is the drum speed 450r/min, the shredding clearance 30mm and the number of cutting tools 10. Bench test and field test of the rapeseed shredding and throwing device were carried out. The bench test results showed that with the increase of the rotation speed of the shredding drum, the rapeseed kernel crushing rate of the shredding and throwing device showed a linear increase trend. Field experiment results showed that the average rate of rapeseed grain breakage was 0.82%, and the operation of the shredding and throwing device was smooth. This study can provide a reference for the improvement and optimization of the structure of the cutting and throwing device for rape combined harvest.