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In order to find the optimal contact parameters combination of alfalfa seed discrete element model, a device and method which can simultaneously measure the repose angle and accumulation angle of materials were provided. The difference between measured value and simulated value of repose angle and accumulation angle were used as indicators to calibrate the parameters of the alfalfa seed model. The Plackett-Burman test was used to screen out the contact parameters that had significant impacts on the index. The second order mathematical models between the significant parameters and the index were established by using response surface methodology (RSM). The nondominated sorting genetic algorithm Ⅱ(NSGA-Ⅱ) was used to obtain the optimal contact parameter combination of alfalfa seed discrete element model, that was, the interspecies collision recovery coefficient was 0.47, the interspecies static friction coefficient was 0.24, and the interspecies rolling friction coefficient was 0.08. Finally, the trough wheel seeder was used for experimental verification. The results showed that the average relative error of the measured and simulated values of alfalfa seed mass flow rate under different seeding wheel speeds was 2.89%, therefore the discrete element model and contact parameters of the alfalfa seed can be used in discrete element simulation experiments, and the multiobjective optimization method based on RSM and NSGA-Ⅱ had certain scientificness and feasibility.