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Aiming at the problems of poor seed filling effect of mechanical seed metering device in high-speed operation and low qualification index of seed metering device caused by unstable seed delivery process, based on the design idea of guiding seed filling and shortening seed delivery distance, a side-guided soybean high-speed precision seed metering device was researched and designed, which realized orderly seed filling, stable and reliable seed delivery by using side-shaped hole structure and guide plate. The process of seed filling, seed cleaning and seed delivery was analyzed theoretically, and the filling force model was established. The key parameters affecting the performance of seed metering device were determined as follows: seed filling inclination angle α, opening angle β; the main structural parameters of the shaped hole were determined, and the qualified index and the missed sowing index were used as evaluation indexes. The simulation test of the seed filling inclination angle α and the opening angle β was carried out by using the combination test method of two factors and five levels of center rotation. The results showed that the tangential filling force reached the maximum value and then decreased with the increase of position angle, while the zfilling force was gradually increased to the maximum value. Seed-filling angle α and opening angle βhad significant effects on qualified index and missed sowing index. The optimal combination of structural parameters obtained by optimization was that the seedfilling angle α was 11.50° and the opening angle β was 119.05°. The bench test results showed that at operating speed of 4~14km/h, the qualified index of the sideguided soybean seed metering device was no less than 95.27%, the missed seeding index was no more than 4.73%, and the damage index was lower than 0.53%, which met the requirements of high-speed precision seeding.