Aiming at the problems that multiple floating debris like sand and broken straw are often sucked into seeding compartments by airsuction seedmetering devices during notillage sowing operations, causing lower seed metering quality, a flexible mechanical type soybean seedmetering device with seedcleaning and maintaining functions was designed. Through a series of theoretical analyses of operation process of seedmetering device, the main structures and working parameters which might affect actual working performances were further determined. And by selecting PE wire, bristle and nylon as seedprotecting brush materials, a series of singlefactor comparisons were conducted, it was showed that there was no significant difference between bristle and nylon in making effects on pass indexes. But PE wire had significant effects upon these pass indexes. As for effects on missedsowing index and repeatedsowing index, there was no significant difference between nylon and bristle. However, PE wire achieved significant effect upon this index. For the damage index, there were significant differences between the above three materials. And through further comparative analyses, by selecting nylon as brush material, adopting 3factor 5level orthogonal revolving combination way and Design-Expert 8.0.6.1, taking operation speed, seedfilling inclination angle and seedprotection distance as test factors, as well as applying pass index, missed index, repeated index and damage index as evaluation indicators, the experimental data was further processed. It was showed that the actual effect degrees of all the above factors which made on pass index were operation speed, seedprotection distance and seedfilling inclination angle from the greatest to the least. Actual effects of all the above factors made on index missedsowing index were seedprotection distance, seedfilling inclination angle and operation speed from the greatest to the least. And actual effects of all these factors made upon repeatedsowing index were operation speed, seedfilling inclination angle and seedprotection distance from the greatest to the least. And actual effects of all these above factors brought on damage index were seedprotection distance, operation speed and seedfilling inclination angle from the greatest to the least. When operating speed was 8~12km/h, seedfilling inclination angle reached 70° and seed protection distance came to be -1.5mm, such seedmetering device can pass 94% of total seeds, and missedseeding index was less than 3%, missedsowing index was less than 3%, and damage index was less than 0.2%, meeting the agronomic technical requirements for soybeans highspeed precision sowing under condition of notillage.