Due to the lack of efficient forage grinders in Chinas animal husbandry industry, a rotary feed tube hammer grinder was designed, and the theoretical model of grinding and rotating feed was established. The key parameters, such as hammer size and shape of, rotation radius, grinding speed, throwing distance, conveying capacity, feeding speed and the length of particles were designed and calculated. EDEM was used to simulate the key factors such as the grinding speed, hammer numbers, tool clearance and discharging angle to grind-Leymus chinensis. Analysis result showed that with the increase of the grinding speed, the increase of the hammer number, and the decreases of the tool clearance, the particle size was decreased, the grinding torque was firstly decreased and then increased, and the particle throwing distance was increased first and then decreased. With the increase of the discharging angle, the particle throwing distance was increased first and then decreased. The optimal grinding parameters of Leymus chinensis obtained by simulation were the grinding speed of 1500r/min, the hammers number of 24, the tool clearance of 22mm, and the discharging angle of 20°. Leymus chinensiswas taken for grinding test, and the test results were basically consistent with the simulation analysis. When the rotating speed of tube was 8r/min, the grinding efficiency of compacted-Leymus chinensis was 25m3/h. The single-person working efficiency was more than 12 times of that of the chaff cutter, and the single-machine working efficiency was more than three times of that of the chaff cutter. The wall-breaking rate of Leymus chinensis-particles was greater than 90%, and the rubbing effect was good. The diameter of particles was ranged from 0.1mm to 1.2mm, with an average diameter of 0.65mm. The particle length was distributed in the range of 16mm to 157mm, the average length was 47mm, and the throwing distance was 11m. The feeding effect of the grinded-Leymus chinensis was better, and the design goal was completed.