Abstract: Accurate simulation of the olive fruits can be often required to optimize the harvesting equipment using the Discrete Element Method (DEM). In this study, the sensitivity analysis of Young’s modulus was performed on the olive fruits using DEM. The geometric model of the olive fruits was constructed to appropriately select the contact parameters. Four varieties of olive fruits were taken as the Picual, Frantoi, Leecio, and E'zhi No.8. Then, 5-, 9- and 13-sphere particle models were established for the olive varieties using multi-sphere modeling. Meanwhile, the rest models were constructed using the automatic filling function in EDEM software. Multi-sphere models were obtained with 13 spheres, as well as the models with the 0 and 2 levels of smoothness. Six DEM multi-sphere models in total were developed per variety. A comparison was then made on the volume ratios between manual-filling and auto-filling models. The volumes of the model types closely resembled the actual shape of the seed particle. Additionally, the manually filled models used fewer spheres, indicating the more efficient model with less complexity. Various contact parameters of the olive fruits were also measured, such as Young's modulus, the static friction coefficient, the rolling friction coefficient, and the restitution coefficient. The rotating hub test was performed to verify the accuracy of the models. A comparison was then carried out on the actual experiment and simulation. The results indicated that the dynamic angle of the repose was increasingly closer to the measured values after experiments, as the number of combined spheres decreased. The optimal number of five spheres was determined for the manually filled models of each variety, in terms of the CPU computation time. Moreover, the stacking test was also conducted on the particle-wall collision. A systematic investigation was then made to explore the influence of Young’s modulus on the movement of individual particles and particle assembly. It was found that the stiffness represented by the DEM model increased significantly, as Young’s modulus value increased. The overlap between particle particles was reduced to increase the stack height. As such, the higher Young’s modulus corresponded to the smaller time step. Consequently, the overall simulation also increased the CPU computation time. Young’s modulus was found to significantly impact the collision behavior of individual particles, in terms of the collision time and overlap between particles. As Young’s modulus increased, the overlap between particle-particle or particle-boundary collisions decreased, which in turn resulted in a reduction in the number of contact points. This finding also highlighted the relationship between the material properties of the olive fruits and their interaction in the simulated environment. Furthermore, the relationship between DEM simulation and Young’s modulus can also provide a multi-dimensional evaluation of the suitability of the models. The contact parameters and DEM models are of significant practical value for the optimization of olive harvesting equipment. The accuracy of these models can be improved under various values of Young’s modulus. These insights can also be applied to the interaction of the granular materials in engineering applications.