Roller conveyor turning mechanism is the most widely used in machine vision grader system. Through force analysis and motion analysis of jujube in it , the horizontal distance mathematical model of jujube from just contact friction was gotten by static acceleration to the same as linear velocity at roller contact point and the rotation angle mathematical model when grabbing jujube images in a certain distance after the accelerating rotation process. Studying the Chinese date of Sinkiang, by determining the appropriate transport speed, position of the camera, and the camera image acquisition frequency of jujube, all the surface information can be gotten, which can ensure the reliability of image acquisition.