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In order to analyze the influence of flow field distribution of cupule type rice seeder on seeding performance, a 2BZQZ-300 seeder was investigated with Fluent software. Models of different nozzle diameters were built and both horizontal and vertical seed were considered in seed suction model. Then, planting experiment was conducted to confirm seed uniformity. The results showed that, the static pressure was well distributed whether above the nozzle or below it, and there was no significant coupling effect of airflow to adjacent nozzles. And when the considered seed was picked up, most airflow appeared at the area between nozzle and seed. The effective stress area of seed surface increased linearly with the increase of nozzle diameter. The negative pressure in the effective stress areas obviously rised with the aperture increasing during horizontal suction, while there were no obvious varieties during vertical suction. Therefore, the seed surface stress in horizontal suction was significantly higher than that of vertical adsorption, which would be helpful for improving the adsorption rate and the stability of seed carrying. The pickup performance was enhanced when diameter of nozzle increased. Because of the coupling effect of seed and airflow, the surface thrust of a horizontal seed was obviously larger than a vertical one, therefore a horizontal seed was much easier to suck up and more stable to carry. As the test showed, seeds were well distributed in trays, and total uniform coefficient reached 94.9%.