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On the basis of analysis of biomechanics of corn kernel and structure of rooster beak, experiment of rooster beak pecking corn kernel on single corn ear was conducted. The experimental results showed that under suitable moisture content, in order to make kernel low damage thresh, the supportive role between kernels must be broken firstly according to certain law. Under the same moisture content, capacity loaded was different for three surfaces of corn kernel. Force loaded at ventro-surface of corn kernel was the largest. The force at the top surface of corn kernel was the least. While choose position loaded, it’s better to avoid top surface loaded of kernel. Rooster beak not only had good ability of inserting kernel cleft, but also stronger ability of pecking corn kernel. The partition that rooster beak inserted corn ear was gap between longitudinal lines. The process that rooster beak inserted corn kernel was the functional process that a triangular wedge inserted corn kernel cleft, that rooster beak inserted same partition could make kernel low damage thresh or loose. When rooster beak pecks lax kernel, it could produce the pull, and corn kernel could thresh, as the pull was bigger than the connection force of fruit handle of corn kernel. This research could provide a bionics basis on improving the geometrical shape of threshing parts and designing low damage seed corn thresher.