Taking a self-developed axial flow threshing and separating device with nails teeth as the research object, the overall process of movement, broken rice spike movement and threshing process as well as the movement process of free kernel were photographed on line in threshing and separating space by using the high-speed photography equipment. Through the slow playing analysis of high-speed video image, it could be concluded that when the rice entered into the threshing and separating space and interweaved together, the valley logistics along the axial spiral surging moved forward under the combined action of the rotary nail teeth and guide plate. The trajectory of broken ear was a parabola and presented to be unstable and fluctuate. Single free kernel without external interference followed approximately a uniform linear motion. Its motion direction formed a certain angle with the drum axis direction.