Abstract: On the basis of the testing system of pneumatic seed-metering device for rapeseed, this paper was conducted to investigate the effect of three factors which are rotational speed of planter plate, rotational speed of fan, and outlet size of positive pressure on the seeding performance of pneumatic metering system of 2BFQ-6 precision seeder for rapeseed. Full factorial experiment which includes 320-times factors combination was used in the course of the study. The data obtained from the experiments were processed by means of multivariate nonlinear regression. The results showed that the factors could be ranged in the order of rotational speed of fan > rotational speed of planter plate > outlet size of positive pressure, the factors which mostly influence the seed rate of the system and its uniformity respectively were rotational speed of fan and its interaction with rotational speed of planter plate. With the increase of fan speed and the decrease of rotational speed of planter plate at a certain range, the performance of system was stable. When outlet size of positive pressure was 20mm and 30mm, the seeding uniformity of system was the best. The equations of seed rate and its uniformity were worked out, and all of the factors combination which makes up 90% seed rate for the pneumatic seed-metering system was drawn in this article. The conclusion is valuable for choosing the optimal parameters matching and estimating the performance of the planter.