Abstract: Abstract: In recent years, corn acreage has became the first place instead of wheat and rice in China. However, corn mechanical harvesting level is low, which has seriously affected the development of corn mechanization. Corn snapping device is a main component of corn harvesting machine, and plays an important role on the quality of harvester. Compared to other kinds of corn ear picking device, horizontal snapping rollers device is easy to cause serious corn grain loss rate and high impurity rate, which has been the choke points of corn harvester development for a long time. Height difference of snapping rollers is a significant factor that affects the ability of horizontal snapping rollers device to pick corn ears. If the height difference is too small, corn ears will stick on snapping rollers after picking, and the prolonged exposure increases corn grain loss seriously. When the height difference is too large, the center distance of snapping rollers remains constant that leads to small horizontal projection gap, and triangular domain shaped by the front cone of the snapping rollers still makes it difficult to feed for corn plant, finally corn plant will bent and broken off, which leads to serious grain impurity rate. Based on the issue of serious gnawing harm and loss of corn ears, experimental research was conducted to analyze the effect of height difference on grain loss. In order to improve the precision for adjustment on the height difference and determine the parameters, the angle between the line of centers of two snapping rollers and the horizontal surface (the angle θ) was employed to represent the height difference. The horizontal snapping rollers device was built, and the grain loss rate was taken as the index to estimate the effect on height difference. Through the single factor experiment, the impact of the angle θ was analyzed. The harvesting process was captured with the high-speed photography, which was helpful to analyze comprehensively in the late period. Through the single factor experiment and the analysis of variance, it was found that the grain loss rate reduced quickly from 24°-30° and changes were small and inconspicuous at 33° and 36°. The average grain loss was the least (0.354%) when the angle was 30°. High-speed cameras were used to collect image datum and analyze the datum. And two phenomena were discerned. It revealed that some corn ears stayed on the snapping rollers after picking, and there was also a "bouncing" phenomenon. Those phenomena caused secondary damage of corn ears and high impurity. In addition, when the angle θ was too large, it was more difficult for corn stalk feeding, which made the corn stalk bending seriously and even to break, and even if the corn stalk was fed, it was easy to cause blocking on the snapping region. So if the large angle is employed, the gap between snapping rollers needs to be adjusted or the snapping rollers can be designed not to parallel with large backend and small front-end to ensure corn plant smoothly. For these phenomena, a curved bulkhead was installed above the low snapping roller. The contrast test showed that the solution reduced the chance of secondary damage to the corn ears. The single factor experiment showed that the grain loss rate reduced at each angle variously and grain loss rate was the least(0.164%) when the angle was 30o. The contrast test showed that the solution reduced the chance of secondary damage on the corn ears. It also prevented the snapping rollers from impacting on the corn ears, thereby reducing loss of corn grain. This study provides a reference for optimization and improvement on horizontal snapping rolls device.