Seed-metering device having multiple cavities and magnetic seed protection assembly

A seed-metering device having a plurality of cavities and a magnetic seed protection assembly, comprising a seed-metering device shell, a seeding plate and a seeding shaft, wherein the seeding plate is rotatably mounted in the seed-metering device shell through the seeding shaft, a seeding channel is formed in the seed-metering device shell, the plurality of cavities are formed in the seeding plate in a ring array, seed filling orifices are formed in one side, facing a seed feed pipe, of the seeding plate, each of the seed filling orifices is connected with a corresponding one of the plurality of cavities, seeding outlets connected with the plurality of cavities are formed in a circumferential surface of the seeding plate, each of the seeding outlets is connected with the corresponding one of the plurality of cavities, a magnetic hinge for closing or opening a corresponding one of the seeding outlets is rotatably connected with the each of the seeding outlets, a notched magnetic ring is fixed in the seed-metering device shell, the magnetic hinge is able to close the corresponding one of the seeding outlets under a magnetic force of the notched magnetic ring, and a magnetic block that is able to attract the magnetic hinge for opening the seeding outlets is arranged in the seeding channel.