Aiming at the problem of poor single seed and uniformity of the existing seed metering device under the condition of small plant spacing and dense planting， according to the agronomic requirements of soybean maize strip composite planting mode， a small plant spacing and dense planting air suction precision seed metering device with double seed clearing function is designed.By analyzing the working principle of the seed metering device and determining the structural parameters of key components， taking the qualified rate， over-seeding rate， and missed seeding rate as the evaluation indexes， and taking the number of holes in the seed metering disc， the outer clearing distance， and the inner clearing distance as the experimental factors， the three-factor five-level orthogonal test is carried out to determine the primary and secondary order and the optimal level of the experimental factors.Through the central combination test， the test factors and levels are optimized and verified.The results showed that the number of holes in the seed metering disc and the distance between inner and outer seed eliminating had significant effects on the seed metering performance； The optimal working parameter combination of corn seed metering is 35 holes， the outer seed eliminating distance is 6.2 mm and the inner seed eliminating distance is 1.6 mm； The optimal working parameter combination of soybean seed metering is 62 holes， the outer seed eliminating distance is 4.1 mm and the inner seed eliminating distance is 1.6 mm.The results showed that the qualified rate of maize seed metering was 95.40%， the over-seeding rate was 1.50%， and the missed seeding rate was 3.10%.The qualified rate of soybean seed metering was 97.78%， the over-seeding rate was 0.32%， and the missed seeding rate was 1.90%， which was consistent with the optimization prediction results， and all indexes met the seeding demand.