This paper analyzed some conditions which cause grain breakage and grain loss during harvesting process of horizontal roller corn harvester. If the transmission rate between two snapping rollers can be changed, the grain breakage and grain loss can be solved at a certain level. So a pair of differential speed snapping rollers for horizontal roller corn harvester was designed, and the work effects between the constant speed snapping rollers and the differential speed snapping rollers were compared by using software CATIA and ADAMS, and found that the rolling speed of inner snapping roller is 500r/min, and the outer snapping roller is 460r/min are the best transmission rate. Finally, a physical experiment was conducted to certificate the simulation effect. In or-der to avoid some disadvantages of field experiment and soil bin experiment in laboratory, half laboratory and half field environment were used in this physical experiment. As a result, the physical experiment confirmed that the analyses above and the simulation by ADAMS were valid. In conclusion, it is an effective method to reduce grain breakage and grain loss by using differential speed snapping rollers for horizontal roller corn harvester.