Abstract: Stevia rebaudiana has high medicinal and health value. In order to speed up the development of Stevia rebaudiana, it is of great significance to study the mechanical defoliation of Stevia rebaudiana. Therefore, an important mechanism of stem leaf separation, defoliator, was studied. According to the self-designed experimental device of the defoliation mechanism, the speed of the conveyor belt, the speed of the brush and the distance between the conveyor belt and the brush that affect the defoliation effect are selected as the experimental factors. Taking the defoliation rate as the evaluation index of the experiment, the influence law model of the three experimental factors on the defoliation rate is established by single factor and orthogonal experiment. Considering the influence of various factors, the best combination of parameters is determined as follows: the speed of the conveyor belt800,the speed of the brush1100,the distance between the conveyor belt and the brush.