Under the influence of medium and high power tractor driving the sowing machine, high-speed precise seeding technology has become an important direction of corn seeder development. So the corn metering device which is the core component of corn seeder attracted many experts and scholars to study. And the results dedicates that the existing pneumatic metering device existed inaccurate sowing precision and the mechanical metering device owns poor adaptability for high-speed operation. According to the above practical problems, a declined disk corn metering device was designed which owned advantages such as simple structure and good seeding performance. The declined dick metering device used angle strengthen sufficient effect and type hole plate to reduce the damage of seeds. The key parameters such as the inclination of the seed metering device and the main structure of the type hole plate were analyzed and determined. Based on the results of the orthogonal rotational combination experiment on the metering device test bed JPS-12, the performance of the metering device was analyzed and the regression equation was obtained between working parameters (the declination angle, number of the type hole, velocity of the type hole plate) and metering performance index. Then the optimized calculation was carried out. According to the optimization results, the speed adaptability test was carried out, the results showed that when the declination angle was 39°, the number of type hole was 30, the speed of the plant was 8.2~11.9km/h, the metering device qualified rate was more than 90%, the leakage rate was less than 3% and the replanting rate was less then 8%, which could completely meet the requirement of technical specifications of quality evaluation for drills in China.