Abstract: According to the thoery of granular rejection intention, the authors theoretically and experimentationly investigated the seed movement laws based on vibration intention parameters on the vibrational air-suction tray seeder. In this paper, a necessary condition of which seeds are to be “boiling” motion was analyzed. And based on this condition, the experimentation indexes both amplitude of seeds injected and rate of seed sucking were used to judge process and degree of the “boiling” motion. When the rate of seed sucking more than 90%, the error between the actual and the critical vibration intention is less than 10%. So the necessary condition is right to be used to design and select kinetic parameters of vibrational air-suction tray seeder.