In view of lack of accurate models for discrete element simulation in the current research and development process of forage harvesting, crushing, processing equipment transportation and cutting, the alfalfa budding stem with high moisture content and complex physical and mechanical characteristics was taken as the research object. With the aid of EDEM simulation software, the physical parameters and bonding parameters were calibrated based on Hertz-Mindlin (no slip) and Hertz-Mindlin with bonding contact models respectively. Based on angle of repose and shear test, physical parameters such as Poisson’s ratio, shear modulus, impact recovery coefficient, static friction coefficient, rolling friction coefficient and bonding parameters such as normal contact stiffness, tangential contact stiffness, critical normal stress, critical tangential stress and bonding radius of alfalfa stem were determined through Plackett-Burman test, the Steepest ascent test and Box-Behnken test. The relative error between the simulated angle of repose and the physical angle of repose was 0.52%. The results showed that the relative error between the simulated shear failure force and the physical test simulation failure force was 0.86%, which indicated that the calibrated parameters can truly reflect the physical and mechanical characteristics of alfalfa stems at the budding stage. It provided a reliable model and parameter calibration method for the discrete element simulation in the research and development process of forage machinery, and also provided a reference for the research and development, optimization design and power matching of the conveying and cutting mechanisms of forage harvesting and crushing processing equipment.