In order to meet the requirements of precision planting, a soybean seedmeter was designed，which can perform operations of seed filling, seed cleaning and seed metering, achieving high efficiency, high precision and low seed damage. The optimal design of structural parameters of the seed-taking block, the key part of the seedmeter, was conducted based on the analysis of the working principle of the double-concave seedmeter, which provided a theoretical basis for the design of high-speed and high-performance planters and variable adjustment of seeding rates by adjusting the rotational speed of the seedmeter. The quadratic general rotary unitized design was carried out with the rotational speed of the seedmeter and tilting angle of the seed-cleaning ring as the experimental factors and the single seed rate as the experimental index. Based on experimental data, a mathematical model was built by using the Design-Expert software. Test results showed that the optimal tilting angle of the cleaning ring was 65°, at which the single seed rate of over 95% can be ensured when the rotational speeds were less than 110r/min.