Main factors affecting the working quality of horizontal snapping roller of corn harvester when it snaps the corn ear were analyzed. By adjusting the spacing between two snapping rollers, the snapping rollers can adapt to corn stalks of different diameters, so the snapping rollers can hold the corn stalks tightly all the time. Finally, the blocks occur during corn harvester working were solved effectively. The grain losses of corn ears were reduced by adjusting the rotational speeds of snapping rollers differentially. Model of spacing-adaptive differential snapping roller was built by using CATIA, and its simulation analysis was conducted compared to the snapping rollers with fixed spacing by using ADAMS software. The optimal speeds of inner and outer snapping rollers were 900r/min and 860r/min which were determined by simulation test of ADAMS. At last, in order to certificate the analyses and design, the field test was conducted. There was no jam occurred during the field test, and the grain losses and damages were both far lower than the national standard which is 5%.