Flax stems contain a large amount of cellulose and have strong toughness. The discrete element rigid model is challenging to express the physical and kinematic characteristics of flax accurately stems in the process of joint harvesting, resulting in the lack of flexible model and contact parameters in the dynamic process of communal harvesting and difficult to micro study. In order to solve this problem, the root, middle, and neck stems of flax were taken as the research objects. The modeling parameters of flax stems were calculated based on the intrinsic parameters. The bonding modeling method of the discrete element method was used to construct the flexible model of flax stems, and the intrinsic parameters and contact parameters of flax stems were set as high and low levels. Plackett-Burman and Central-Composite tests were used to determine the contact parameters between flax stems and harvesting equipment. 〖JP3〗The flax stem shear test and stacking angle test were used to verify the model's reliability. The results showed that the normal stiffness Kn=1.13×109N/m3, and tangential stiffness Ks=5.6×108N/m3 in the flax flexible model parameters. Normal critical stress σ=6.67MPa, tangential acute stress γ=8.5MPa,bond radius Rj=0.25mm. The optimal values of recovery coefficient, static friction coefficient, and dynamic friction coefficient between flax culm-steel parts were 0.33, 0.28 and 0.14, respectively. The optimal values of recovery coefficient, static friction coefficient, and dynamic friction coefficient between flax stems-flax stems were 0.3, 0.508, and 0.033, respectively. In the shear test, the relative errors between the maximum shear load and the simulation results were 1.67%, 3.09% and 5.44%, respectively. In the stacking angle test, the relative error between the average stacking angle of the stem and the simulation results was 0.31%. The flexible modulus of flax stem was consistent with the contact parameters and the actual situation. The physical properties of flax stem can be characterized. The research result can provide some reference for discrete element simulation of flax stem.