Abstract: In order to improve seed-sucking performance of air-sucking seeder, seeds should do slung-up movement on the pan on the condition of excitation. With vibration of the pan approximately being single frequency, the conditions that make the seeds sling up were analyzed, i.e., the component force in perpendicular to slot base of inertial force of seeds should exceed the one of gravity in the perpendicular direction to seed disk(It can be carried out through the adjustment of pressure valve). The theoretical condition has been validated through experimentation. The results show that to make the seed to do sling movement, the index D of sling must be larger than 1 and usually its range is from 1.4 to 3.3. The radical frequency of stimulating vibration has a lower limit. Only on the condition of favorable matching of frequency and amplitude of the vibration, can sucking-seed part develop the favorable sucking-seed and pegging-seed ability for seeds slung up.