Based on the principle of vibrational air-suction, seeds will be “boiling” state in the vibrational air-suction tray precision seeding-machine, which can reduce the inner friction force and increase the capacity for sucking seeds motion. According to the granular rejection intention theory, we theoretically studied the seeds movement and calculated out a critical intensity of vibration of the tray precision seeding-machine in which the seeds would be “boiling” state. The results show that when the rate of seeds sucking is more than 90%, the error between the actual and the critical vibration intention is less than 5%. So the critical condition is right and it can be used to ascertain the operating range of vibration parameters.  