The flow field has significantly impact on seeding performance in the suction seeding device. A three-dimensional, incompressible, viscous, RNG turbulence model and the SIMPLE method were used by computational fluid dynamics(CFD), and the flow fields of suction cylinder-seeder with different socket’s radiuses were simulated by Fluent. When vacuum is 4kPa and productivity is 350 trays/h, the simulant results show that pressure is uniform, velocity is stable, energy loss mainly occurs near slots and outlet, and there is less interaction among socket-slots; The effect of flow field on socket’s radius to the cylinder isn’t significant by contrasting different socket’s radiuses on the average turbulent kinetic energy, the average vacuum and the maximum difference of velocity behind slots; The experimental results show that the best seeding performance is 84.73% when the socket’s radius is 5.5mm. Although the performance should be improved, but any sockets are never plugged, which shows enough that the seeder is a very promising precision seeding device.