Abstract: The theory of seed suction performance of vibrational air-suction tray seeder was analyzed in order to promote the exploitations and applications of precision seeders. When seeder tray was approximately vibrated with single frequency and the air resistance was ignored, the seeders tossed were "boiling" to reduce the inner friction force, which increased the capacity for sucking and fixing seeds. The air flux was then thought equal entropy flux, therefore the mathematical model was obtained. The result of experiments is basically in accord-ance with the mathematical model. At certain vacuum, the capacity for sucking seeds is raised with the increase of sucking mouth diameter, but the sucking mouth diameter must be less than the seed diameter. The quality of sucking seeds is improved with the increase of vacuum in the sucking mouth. With comparatively smaller vacuum, the effect of vacuum on the height of sucking seeds is conspicuous and the effect becomes less with the bigger vacuum. The vacuum has a limit value of 48 kPa, above which the quality of sucking seeds cannot be increased. The height change of sucking seeds tends to be distinct and uniformity with the increase of sucking mouth diameter at certain vacuum.