The utility model relates to an automatic metering device of a single-plant soybean thresher. The automatic metering device of the single-plant soybean thresher comprises a box body, wherein a micro-computerized controller, an seed-receiving box, a split type weighing box, a weighing sensor and a drive motor are arranged in the box body; a seed distribution fixed plate is arranged on a bottom part in the seed-receiving box; a seed distribution movable plate is arranged on the seed distribution fixed plate; the upper end of a main shaft of the drive motor is in transmission connection with the seed distribution movable plate; a support is arranged on an inner wall of the seed-receiving box; discharging holes are arranged in the circumferential edge of the seed distribution movable plate; seed scraping brushes contacted with upper edges of the discharging holes are arranged on a lower part of the support; a seed discharging pipe communicated with the discharging holes is arranged on a bottom part of the seed-receiving box; a photoelectric sensor is arranged on the seed discharging pipe; an outlet of the seed discharging pipe is located above the split type weighing box; the split type weighing box is arranged on the weighing sensor; and a signal input end of the micro-computerized controller is respectively connected with a photoelectric measuring device and a weighing measuring device. The automatic metering device of the single-plant soybean thresher is arranged on the soybean thresher and is used for metering after threshing, has no damage to seeds, is quick and accurate in automatic counting and weighing, has a memory storage function, and is convenient to check and process after test.