Abstract: Ball-spoonshaped inner-cell vertical-plate metering device can meet the requirements of the crop of single grain sowing or the crop of fixed quantity cave sowing. The seeds discharged by the metering device should not be injured according to the theory of delivering seeds. From the experiment results of the seed-plate, the seed-injuring rate is higher than the index of the national standard. How to reduce the seed-injuring rate is the main problem. In this paper, the motion equations of seed were established, and then the mathematical model of main parameters were established through computer simulation of clearing process, optimal design of parameters of the device was laid and seed-injuring rate was reduced.