In order to study working parameters’ effect on flow field distribution in side positive pressure seeding device, LES (large eddy simulation) of Fluent software was used to analyze positive pressure flow field in seed-metering device. Simulation analysis and contrast experiment for positive pressure flow field were performed under different working parameters. Results showed that pressure field changed slightly in seeding device with increase of plate rotation speed when inlet pressure was set. According to velocity field, performance of seed metering was poor due to higher plate rotation speed. When plate rotation speed was set, pressure variation had non significant effect on seeding performance. According to seeding experiment results, seeding qualified index reached 91.30% when inlet pressure was 1.2kPa and plate rotation speed was 16r/min. Rotation speed of seed-metering plate was the significant affecting factor of seed metering performance.