Abstract: The rationality of technological process for 5JDF-0.5 dielectric seed separating unit was demonstrated in this paper by means of analyzing seed cleaning and separating principle. Experiments of separating rape seed and Chinese cabbage seed were made by means of the unit under the conditions of different electrodes and different separating voltages. The results showed that seeds can be graded in terms of both 1000-grain weight and vigor by the unit, and different separating effects can be obtained by adjusting the separating voltages.